Q: Brake Pedal feels loose have to push all the way down pumping it helps stop it but mostly it keeps sliding until I pull E-brake.

Recently had my friend change out my brake line hose but now when driving it the brake pedal feels really soft and goes all the way to the floor when I push down so I have to pump it a couple times and occasionally it'll stop but mainly it just barely slows down even when im pushing down as far as I can forcefully it slowly keeps moving I check my fluids and make sure everything is good I was told he may have put transmission fluid instead of brake fluid but idk if that's the case. Its just easy to push with no pressure and hard to stop, also the plastic black thing that goes in the brake cap to seal it is broken and isnt closing fully. He's slammed on the pedal a lot when mad putting wear and tear on it. Could it be possible that he did put the wrong fluid and it caused a tiny leak or air in the hose or maybe the master cylinder going out from the hose being put on wrong and wearing the suspension out making it not have enough pressure it needs to stop the car?

My car has 188936 miles.
My car has an automatic transmission.