I would advise doing lvl 1 again, followed by 2 and 3. When you're able to finish lvl 3 then continue upward.
When you fail again, say at lvl 5 then start again from 3 and going back up.
Reason: some levels have different exercises which adress other muscles and doing the same lvl again and again might leave you bored or annoyed at the lack of progress.
Just give it your best every training and you'll move up the ladder.