Henoest

So i was going to my car in the afternoon and key fob was not opening any locks but rear hazard lights blinked as it usually does(not front however) after manually opening the driver side door with the key inside the fob i tried to start the car. Almost nothing happened, no dash lights but the headlights came on and lights in doors and such works fine, radio as well. Car did nothing else, i tried the START/STOP button and inserting the key fob but still nothing, figured it was an old battery as i have no clue when it was last changed so i bought a new one and installed it no problem. The car tried to start this time, it turned but never once actually started. I have no clue what to do or what could be wrong, im quite dependant of my car to pick up kids from kindergarden as they live quite a while away so this is quite problematic for me. i would really appreciate some thoughts First post so dont judge too hard :) Thanks