The guy who passes you is the guy you need to ride with. It may come down to fitness and youth, but he may also know something you don’t about technique, line choice and where to spend his energy. That section of trail that sucks your speed may be something he flies over without touching and that keeps him fresh for whatever he passed you on. Don’t let getting passed compel you to upgrade your bike, most of the time it is not the bike limiting you unless you are at some downhill park so I would scratch that one.
Ask if you can follow him and watch his lines, remain competitive with yourself and use him to gage your progress. I keep track of features on the trails that slow me down and try to improve on the slow points. I also pay attention to how long it takes me my lungs back after I attack.
I guess what I’m saying is being Type A and not being the fastest is possible and enjoyable with the right perspective.