How do I figure out what the problem is?

What is your question?

Not to long ago the hose for the coolant collapsed and came undone and all my antifreeze and stuff went everywhere. We fixed that but ever since then, the gage indicates that the car is overheating but it isn't overheating. Then a new problem acured with that, it would start to shake and lose all power and she would be stuck in gear when the gage indicated she was hot.