Natsu-Dragneel became a Primordial God when the last primordial gave him his position and all of his power. This happened after Natsu died and became E.N.D, since Natsu became the primordial god his book which held as his life line (I'm talking about the books Zeref which held Natsu-Dragneel or E.N.D's life or existence was destroyed from the infinite ♾ power of him becoming a primordial god, but because he is a primordial god he didn't die he absorbed the book of E.N.D and gained it's form and he could control his new form easily if he wanted too he could change into the new form anytime he wanted.(Now you're probably wondering how did he control this unlimited power and become the Ultimate Primordial Dragon God King/Dragon Slayer, well put it simply he was trained by every dragon and dragon king as well various other people in different universes and multiverses "(he'll travel to other universes and multiverses a lot later)",but that's The answer to the second question now I'll answer the first question, the former Primordial God gave him everything his knowledge his experience and thoughts and personality, but Natsu-Dragneel still needed to learn how to control all of the powers and transformations himself as well so the former primordial god had locked the various abilities of all the different types of bloodlines and their abilities including their transformations and race, but he did have complete control over life and death,space and time and all of the other elements, but he'd still have to have a teacher for all the elements,except life,death,space,and time, in each world he'd have to learn and do everything the former primordial god did, but the difference is the former primordial god had control over everything so Natsu has to start off at a different point on the gigantic spectrum, he will still have complete control of his E.N.D form and the other bloodlines,abilities, and transformations once he obtains them.)
Once the former primordial disappeared Natsu had limitless potential he felt no pain and he's Immortal with Instant regeneration and anything he see's once he can do it better than the person that taught him he also had complete mastery over all weapons.
Natsu saw a bunch of dragons and dragon slayers heading his way while his head was in the clouds yes it's a metaphor. The dragon kings and dragon god kings and some other known and unknown dragons there were also other races that were in the front that consisted of Acnologia, Igneel, Metalicana, and Grandeeney, Weisslogia, Skiadrum, Zirconis, Atlas Flame, Irene Belserion, Belserion, Scissor Runner, Motherglare, Levia, Animus, Elefseria, Mercphobia, Selene, Aldoron, Viernes, and Ignia. Behind them were Erik, Gajeel Redfox, Georg Reizen, Kiria, Laxus Dreyar, Madmole, Nebaru, Reiss, Rogue Cheney, Skullion Raider, Sting Eucliffe, an Wendy Marvell, God Serena,Dark Dragons, Rock Dragons, the quartum army's, Wolfen, Metro, Gears, Doom, Eclipse Loke, and lastly Zancrow. They were running towards Natsu because they sensed an surge of magic power to the extremes. When Natsu saw the dragons, dragon slayers, god slayer, dragon kings, god seeds, and lastly the dragon god kings he smirked that looked like the Demon King himself once did this every felt a shivers down their spine, but they came towards him and tried to attack him. When they attacked Natsu he punched the with overwhelming physical strength alone and they were all sent flying back about a yard or two when they all regained consciousness Natsu was directly in front of all of them then he let out his bloodlust and when that happened all of them were kneeling in fro Natsu who was laughing.
He then told them all too teach him everything they know and then give him their Ethernano attack that they can only use once in a lifetime and then after that attack him with it so he can absorb all of their attacks and become more all powerful or else. After that some of them, said no. Natsu-Dragneel stomped on the ground and made an earthquake and some of the rock and shadow dragons died just like that. Afterwards the they all complied because they were afraid the same would happen to them. Acnologia went first, then Igneel and Ignia, next were Metalicana and Mercphobia and so on. Once everyone was finished Natsu told them who he was what he was capable of and what he would do. To say they were shocked would be an understatement. What he would do he would give all dragons a human form with them having complete control over it, he would as give dragon slayers a dragon form with them having complete control over it and then not being able to lose their sanity or anything like that he would also give them immortality in exchange he would make it to where they could never betray or disobey him and they would voice their opinions on important matters. They all said yes, next was Zancrow he would give him immortality and make it to where he could never betray him. Once that was finished he beat Wendy, Kiria, Irene and Grandeeney so that they would become his mates he also said they will follow him for an eternity wherever he may go till the end of time (not romantic like) he didn't mate any of the boys or men, but still told them to follow him wherever he goes they all immediately said yes, but they first asked him to make it to where all dragon slayers never lost their sanity or anything of the like and to put a barrier around the dragon kings palace he said yes, but after that he told them where they were going and who they were going to meet there to when he told them they were gobsmacked because they were going to meet Zeref and because of this acnologia was furious, but obeyed nonetheless when Zeref saw them all especially Natsu-Dragneel his little brother he cried and told them all to stay away everyone did except Natsu he quickly showed up behind him with "chaotic void" and with that Zeref fell down on his butt and then Natsu released his brother's curse and made him immortal again straight after and then told him what he wanted him to build to and when he did Zeref was intrigued and did what his brother asked which was to create the Eclipse gate and they all went through they came out on Tenrou Island and when they they all saw a little girl this little girl was Mavis Vermillion as soon as Zeref saw he asked his all powerful little brother to make her an immortal and he did on the condition him her get married to which Zeref happily said yes.
"(Mavis's point of view)"
What are dragons doing here not to mention so many and who are those two people at the front. I guess I should go welcome them to the island, said Mavis while stuttering.
"(Back to Natsu and the gang)"
"(I'll mostly skip everything else except for a few things that happen in this world.)"
"(Okay I'll just skip most of the fairy tail storyline.)" (time leap to when Erza is at the tower of heaven they immediately rescue Erza while being marked as one of the mates for Natsu-Dragneel,"(time skip again to when Lisanna and Mirajane are about to go on their first S class mission with their big brother Elfman Natsu knocks Elfman out and shows Lisanna and Mirajane what would have if they went on this mission after they see everything they immediately start seducing Natsu like this.
Natsuuu💗❤️💘 said Lisanna and Mirajane rubbing their hot thighs and sexy long legs while they were doing this Natsu started kissing them like there's no tomorrow while this is going on they start taking off their clothes Natsu wearing all black except a white scarf and his black scarf as well, next is Mira who was wearing sexually sexy black thongs a black bra and black panties they all completely complimented her sexy body, next is Lisanna and provocative black bra, thongs, and black panties as well they took that all of that off well the black thongs and knee socks they Mira was suck on Natsu dick while Lisanna was trying to kiss Natsu, but Natsu has other plans and started sucking on her tits and fingering her clit which was as sexy as her as this was happening Lisanna started moaning Natsuuuu❤️finger my clit more harder ahhhh❤️ Natsu I love ❤️ you said Lisanna. Then Natsu started shoving his dick up and down Miras throat until he came inside her mouth she licked it all of of dick the parts of the semen that didn't go down her throat she then said thankssss❤️for the Meal Natsuuu❤️seductively. He then asked Lisanna to let go so he can fuck her sister and she said yes Natsu my darling seductively. He then picked Mira up and shoved his dick inside her clit and started ramming it in out and Mira started matching their rhythms in harmony Mira started moaning until the both came at the same time then Lisanna and the same thing happened. After that he put a spell on Elfman to where he would have a brothers-in-law which is Natsu. They were going to the fairy tail guild and Natsu kicked the front door off the hinges into Cana Alberona who barely managed to avoid it. (If you're wondering yes Mavis and Zeref were the first Guild-Master's not including Natsu an the gang). Natsu being one of the first Guild-Master's not too mention him being the Primordial Dragon God King they were all shocked except Zeref and Mavis who greeted them. Natsu demonstrated his power by making Makarov young again and giving him immortality as well he the Levy McGarden as another mate and Cana Alberona he then went to make Angel and Ultear and Meredy plus Ur his mates as well and when he had sex with them one at a time they were all sexy and seductive in their own rights.(Not including Mira, Irene, Wendy, and Kiria). He then went to go make Hisui his as well and might I say her body was divinely sexy. Space jump to another planet with everyone of his mates including Hisui and his followers note they all are in their human forms.