It sounds like you're applying far too much pressure with your fretting hand, although much of that could be from the string height. Try to relax more.

How you position your fingers when fretting will vary: sometimes you need the '90 degree angle' so that you don't accidentally mute the strings on either side, other times you may deliberately want to mute them, but that all comes with practice and experience.

Pros make playing guitar look easy, but they've spent thousands of hours getting there.

Shoot the inner critic and just have fun learning... (I'm at a point where I can pretty much play what I like on an acoustic, but make loads of unwanted noise when playing electric. I'm not worried about it, though, because I know I'll get better with patience)