Hello. What do you mean sexual capacity? Do you mean maintaining your erection longer? You can check out this link. It is about how to get a harder erection. https://www.medicalnewstoday.com/articles/how-to-get-harder-erections#diet A lot of it is just good for you things like healthy diet, exercise and proper rest. But it also talks about communication with your partner and trying new things. Limiting your alcohol and smoking helps and stress can play a huge role in our sexual experience. Reducing your stress if you are under any would probably help too.
For lasting longer before erection, that can be a mind thing for some guys. Might have to disengage a little. Not so much that you lose your erection but enough that you don't ejaculate too quickly. Fine line. https://www.healthline.com/health/erectile-dysfunction/how-to-last-longer-in-bed-naturally Here's another readable for you on that subject. Of course there are medications that help but if you do not want to go that route, the article has suggestions. There are some supplements and herbs you could try. Mostly though, it's controlling the mind and stopping and starting stimulation to last.
You need to be more specific. Enjoying sex isn't really about how large you are, we are who we are. It much more about the degree of mental involvement one is able to have, how much focus, and how much one learns over time about how to do it in a way you and your partner like. But it's mostly mental. You can't really get drugs to get a better erection unless you have a medical problem, unless you buy them illegally, and since they have side effects I wouldn't recommend that. There are recreational drugs that enhance sexual pleasure. There are as mentioned natural supplements meant to supply what your body does naturally in case it isn't working optimally. But again, you don't mention in what way you want to enjoy sex more of if you're having some problem that's getting in the way. Truly, a lot of sex is based on how much you're into the person you're having sex with and how much they are into you and how much both of you are into sex -- a lot of people really aren't that interested in it. That's assuming you don't have a health problem that is getting in the way or taking a medication that is getting in the way.