Hi there!
I lived while I was small in the US for 4 years.
At the time I had a green card.
Can I get a new one without all the trouble?
Does it matter at all if you already had a green card in the past when you want to apply for a new one??
Thx

Assuming that you haven't lived in the US for years, you are not a permanent resident any longer. You can apply for GC just like anybody else. Your former status as LPR has no relevance today.

When di you leave the US.

How old were you?