[subject] + wish + [subject] + [past simple]
[subject] + wish + [subject] + could + [verb]
I wish talks about something you would like to be true now, but it isn't. The verb after it goes one step back into the past, even though the meaning is about now.
With be, you can use were for every person. I wish I was is also common in speech.
Use could for something you aren't able to do.
Wish + would is about something you want to change but can't control, often another person's behaviour that annoys you. You don't use it about yourself: say I wish I could, not I wish I would.
For something in the past that you are sorry about, use the past perfect (had + past participle).
Hope is for something that can still happen, and it takes a present or future verb. Wish is for something that isn't true.
After wish, the verb doesn't stay in the present.