Okay this happened to my boyfriend and me, so maybe I can advise. He could make me cum but he kept going soft. Turns out the condom was too tight and he wasn’t well lubricated inside. My advice? Foreplay, foreplay and more foreplay. This time she needs to do everything that she can to turn you on. Sloppy kissing, sloppy blowjobs, you have to feel comfortable around her, you have to learn to breathe, be hydrated, be hella wet, get rubbing and then apply lube. So much lube. It’s just as important
For men as it is for women! Get water based lubes. They usually do the trick. Then on top of it get blowjobs. The mix usually helps. Also try to watch porn together or do something erotic that involves her not touching you immediately or you not touching her immediately. Use toys if you want to. And use slightly bigger size condoms. Some brands can be too tight and reduce blood flow down there so you need something breathable. Try mutual masturbation or masturbating in front of each other.
Make out naked. Cuddle naked. Get realllly well lubed before putting the condom on. You want both natural and synthetic lubricants. You also want to make sure the condom is made for both your pleasure. Not just one person. And try not to cum or jerk off for 3-4 days before you see her. It’s going to be hard but you neeed the tension and build up right now since you’re learning about each others bodies.