it can be difficult to settle on an idea! honestly i would say figure out which idea you like most so far--anything that you just feel like you're really latching onto whether it's a narrative element or some kind of mechanic that you think is really interesting. from there, i would write down all the mechanics or assets you think the idea would need--pretty much anything you can think of! then circle the absolute bare bones of what you would need to make the most basic game--while still including that one thing you really like. even if this approach doesn't work for you i think just making decisions and being okay with making a game that isn't perfect is how you can start to conquer decision paralysis and learning things so you can be more confident in your decisions! i'm wishing you the best of luck!