Can you trust someone who has already betrayed you once before?

probably not unless they genuinely changed which usually they haven't

Yes, I mess up and hope they would understand.

I have tried to do that when someone did that, and they explained they were working on themselves, going to therapy, etc. I was an idiot and thinking, "I've known them for years. Their family life was a mess like mine." It wasn't until I started to heal myself that I saw they were never going to change. Just suppress themselves to trick me.

Betrayed means something very personal that hurt and embarrassed you and they intended to do it for that reason. I would save never they lost my trust!!

Yes, we are all f*ck ups who make mistakes, buttttt everyone has their own boundaries..

Some people won't forgive anything, like as if they're perfect or something

no