I feel so behind. Never been one to do much during my teens and early 20s. But now i want to party and go on adventures at 26. I feel like im too late

You just need to pick the right places to party at. Obviously you'd feel out of place surrounded by teens and 20 somethings in certain bars and clubs they frequent. And equally you shouldn't surround yourself with people who keep telling you you're too old for those things. You need the right crowd.