Car won't start

What is your question?

Hi my car I bought it used I was told it only needed a thermostat the car runs hot. now it won't start the battery symbol pops up. One time while driving it wouldn't accelerate I could only go 5 mph what should I do about all this ?

What makes this problem better or worse?

Moving the car at all makes it worse.

How long has your 2003 Volkswagen Beetle had this problem?

I've had the car for 1 month.