Q: Car dies when trying to start

Greetings. After pressure washing the engine bay(not by myself, but by professional), I managed to start the vehicle pretty easily. But after driving 15 miles and turning the engine off and starting it again, the whole electricity died. When i remove the positive terminal from the battery and put it back on, electricity goes back again, but after trying to start the engine again, it just dies again. I can jump-start the vehicle when someone tows me, but the electricity goes dead again while driving if I turn on something that consumes a lot of energy like high-beams. I have a faulty starter(sometimes the engine starts easily, sometimes I have to turn the key few times, because it doesn't spin), so does it have anything common with my problem? Maybe pressure washing killed my starter completely? Thanks for your help!

My car has 180000 miles.
My car has a manual transmission.