Hello dear players,
I want to know does after time limit ends my dragonballs gone or back to my bag?

Dragon balls you collect on the weekends stay in your inventory until you summon the dragon, if you only get 2 one weekend and 3 the next you'll still have 5. You can do it in parts if you like instead of trying to get all 7 in 3 days.

Yep, if you run out of time they go back in your bag. You won't lose them.