"If you created me, who created you?"

"you are my creator, yet you will die but I'll live".

"Their species are dying"

Alien Convenant is more about David than alien itself.

Got questions about this movie but later on Ill post.

Aliens in Predator universe are not the same as alien in the original Alien universe. Aliens in Predator 2 and AvP series are in diferrent non canon universe where the studio just wanna mash up both species fighting each other in 1 movie based on fans request and Dark Horse's AvP series.

I also believe the alien Xenomorph and Alien queen already exists waay before David developing his Xenomorph. Its because the Alien Queen's figure was already etched at the Engineer's armada ship. My theory is, David may found that the Xenomorph was previously developed by the engineers based on the scrolls and research he founds when he was stranded with Shaw at the Engineer's planet. David maybe simply wanted to recreate back the xenomorph, which the Engineer's don't want to create.