Not starting properly

Before my car broke down, it would sputter while driving and either not change gears quick enough and kind of jump or slow down while I was accelerating as if I was braking. Then took it to AutoZone one day it started automatically braking, the gas and brakes went out, (i recently had the brake lines replaced and they were doing fine) all the lights on the dash came on, and the steering wheel locked up to where it was getting really difficult to turn had to use all my strength and use the e-brake to slowly come to a stop. I had my neighbors tow it to my house where’s it sat for two months or so.
So far, we’ve replaced the alternator, spark plugs, fuel pump, and ECU, and I’ve taken the battery to get examined and it’s perfectly fine, in that order. The car is still doing the same exact thing where it will turn with the key and want to turn over, but when it reaches the point of running you know when you turn the key all the way and it starts so you let it go, it’ll stay on for like a single second and then it’ll falls flat on its face. I cannot figure out what is causing this to happen and I’m trying to avoid spending dollars upon dollars of money that I don’t have by taking it to a shop. So, I’ve done everything myself, but now I might have to have it towed somewhere. I’m a 20-year-old girl that pays bills and takes care of myself and this is my first car, and it’s putting me in a bad debt position trying to get this thing to run, so, if there are any tips or tricks or you know what’s up, please let me know ASAP. Thank you