You should brainstorm for a while until you have a game idea you're comfortable with and that also isn't overscoped.
Maybe get in a call with some friends and just talk about your current idea and see if they have any suggestions you could add.
I recommend using something like Milanote or Miro as a whiteboard, or just a piece of paper if you prefer that.

Take it this way my man, there are a lot of people like you that are struggling and especially in the instance that you may not have a lot of experience it might demotivate you a little but remember that game jams are there to learn. I for one just had my entire windows install corrupted and lost everything that i had worked on. Just take it at your own scope try to make something that you enjoy doing challenge yourself and just have fun with it. Also as a quick note trello is also a really good platform for managing your goals and what needs to be completed and im sure you will definitely grow as a developer.