serious brake problem..

ok, so my brake fliud started going fast on my master cylinder, turns out my front left brake caliper was leaking, so i get a new caliper and put it on, bled all the brakes. When the car is on the brakes go all the way to the floor before they work, and when i was going about 30 mph and testing them, i slammed on the brakes and the left rear brake locked up. I dont see any leaks anywhere. I need to fix it fast cuz its my daily driver, i also cant pay 300 dollars at a brake place. If u can help, please do. Also even when i dont slam on the brakes it takes them forever to stop.

Okay you either didnt put enough brake fluid in.
If you filled it once closed it up everytime that you pump on the brakes it sucks fluid down so you got to keep pumping and then fill it. Keep repeating that

Or you have air in the lines that didnt get bled uout properly.

its got fluid, so i think i screwed up bleeding the brakes, it was my first time to do it.

If i remember you def need 2 people to bleed it. One to loosen and tighten the bleed screw and one to pump the brakes.

i did have two people, my friend was pumping the brakes.