2007 Mitsubishi Galant

2007 Mitsubishi Galant. My son was driving his car and it just died going down the over pass. We were told it was the alternator & battery. $300 later we changed it and it still won't start. When we put the key it in clicks a few times, we try starting and it struggles to even turn over. We have lights. Now I'm told it could be several other things. I can't afford to fix every suggestion. Someone that knows this car please help!