Need help with 1973 super beetle

I just bought a 1973 super beetle and i do not have any mechanical knowledge except that i can put oil in it.  the problem is that when i get home after driving for maybe an hour at the most and then try to start it up again it doesnt turn over but all the lights on the dash turn on. so i go to push start it and it does start but i have to keep my foot on the gas for 20-30 seconds or it will die.  i would like to know whats wrong before i get ripped a new one at a mechanics shop.  thank you in advance.