After getting your car repo is it legal that they keep your belongings such as rims and radio?

That's not important. What's important is that you don't have a car any more. Now grow a brain and don't ever buy a car with payments again. Walk or ride a bike until you save enough to buy a car with all cash and no payments. Try to buy one like the taxis use. Pay a mechanic to inspect it before you buy. Don't do any repairs. If something breaks, sell it and buy another that hasn't broken yet. That is the cheapest way to own a car, and even at that it costs around two grand a year to own it. You can save a lot by just getting a job closer to home so you can walk to work.