I have to move to Poland for at least 7 years for my fiance to achieve her academic goals.
Is she still in high school?
What are my chances of getting a good paying job there?
Not high. You might get a job, but it's unlikely to be well paying.
I want to support her but I worry I am ending up to be a hindrance instead of support.
You certainly will be a hinderance if you're much older than her and hanging around her the whole time.
Given your previous threads (particularly the fact that haven't actually met this 'fiancee' of yours in years) - I suggest you should take things one step at a time.