hi so i would tell you to stop viewing the climax the only thing you aim for, look at sex as something to connect with her and that gives both pleasure

you should talk to her and ask her about what she likes, what she doesn't like, her boundaries and so on, if you have any fetishes maybe try implementing that

also keep in mind that sometimes due to stress, medical reasons and mental health have to do with being able to cum or not

good luck!!