How can I regain my ability to finish?

Okay so I’ve quit porn for about two months now and I’ve gotten a girlfriend recently, since I quit porn I can finish and I do it only to my mind however it’s very hard to finish if I’m talking to my gf it helps but I have to go stupidly fast in order to finish and have a hard time finishing even with her help. How can I make it easier for myself it finish? Or is this just a matter of time?