Is my decision correct? I always gave up when I have exactly a king, one knight, and one bishop, while my opponent had a king, one rook, one/two knights, and two/one bishops (respectively). Is my decision correct, because I felt I cannot do anything with those 3 pieces, while my opponent had those 5 pieces.
If you feel that if you could change seats with your opponent and play his side and win then your decision was correct. He was good enough to get such a big advantage. If you could win from his position then, likely, so can he.

If, on the other hand, you don't know how you would win if you could swap positions, then don't resign. It could be that he doesn't know how to win either. Instead try and work out how to make his task as difficult as possible. It may be that you can get a draw.