how long does the game have to be? 

like 10 levels or as many aas i can get done in the time limit?

sorry new to game jams.

(first one for me too) I think it doesn't matter, but the videos I watched said that you should prefer making a short, good game than a long, bad game & dont overscope!

I've seen lots of games go for replay value over length. So arcade-style games like Asteroids or Space invaders, were there aren't really levels, but rather the difficulty ramps up over time work well. Games that go for length usually have like a couple of levels that are short and intense. Overall most games are like five-to-ten minutes, at least from what I've seen

10 levels is honestly quite a lot for a jam unless they're like one screen each. Rather than making as many as you can, I'd recommend just doing the least necessary to show off your game.