had a mechanic look at my car because it wouldn't start. after a few inspections he told me fuel wasn't getting to the engine and was probably a bad fuel pump. i replaced it myself and connected everything back the way it was. tried starting and got no result, excpet for a part of the fuel line i forgot to tighten started to leak near the the tank. so the fuel pump must be working and i have no idea where else to look...

There are a lot stuff that could go wrong to cause starting problems. Basically for an engine to run, it needs 2 things - fuel and spark.

If it happened suddenly, could be electric - spark plug wires, ignition coil, etc.

Otherwise, could be your fuel pump. You can try have someone crank the engine and you smell the gas from the tailpipe to see if you can smell any fuel.