2000 Mitsubishi Space Star Car not starting

Hi, 3 days before I drove my car 2 hours and parked at hotel where I work. After finishing work I started car, the car did not started. For first one /two second it gave cracking sound (as it used to give when starting). I called to my friend. He helped me. He cleaned the the rust(acid diposited on the battery terminal) from the battery. Still, the car did not start. Then, he started his car and Connected positive terminal of battery of his car to positive terminal of my car and did same for negative terminal by extra connecting wires. (Recharging). Then the car started. He removed Connections from my car, my car is starting. Then, I stopped car and restarted, but the car did not start. Again, he took the connecting wires from the battery terminals of my car out and cleaned very fine, all rust has gone. Then, he started the car. Then the car started. He pressed the Accelerator pedal and heard the sound. He said sound not usual and battery needs more charge. So, I let car With starting condition for 15 minutes. Then, I stopped the car. Then the car started. I did starting and stopping 2/3 times, it was ok and used to start. But, NeXT day when I started the car, it did not started. This time also, the tried to start for giving starting sound, but it did not start.