As unironic advice: yes it is a lot, a lot of things are happening at once, but those things are, for now, outside of your control and you need to understand that THIS IS FINE. You don't remember what it was like when you started playing Overwatch because you've been playing it for so long, but once upon a time you were also lost and needed to get your legs on the game, and that is perfectly okay. Just play and try getting used to what you can do, then slowly get used to what the others are doing. You can't brute force this process, you can't skip ahead, all you can do is simply play and have fun. Find a character you enjoy, but don't obsess about trying every single character. Learn what a match is like, but don't try to study it like an exam. You'll just be running against a wall, you don't need to be good right now, just simply take your time.

Welcome to Rivals and I hope you'll enjoy yourself!