So my SO's grandma let me use her car to take my son to school today. I was grateful I got him to…

So my SO's grandma let me use her car to take my son to school today. I was grateful I got him to school but I did notice her car running pretty hard the check engine light was on and it smelled of burning rubber anyways her breaks aren't very good either. So as I'm making my way back home I'm going up a hill going the speed limit 40 and luckily I always break early so as I'm trying to break the car isn't breaking so I slam my foot already down and nothing I had to drive off the road into a grass hill and throw the car in park as it was moving to stop it. So I go to give the car back and my SO doesn't wanna tell her about this for idk what reason. But he asks about the breaks to her and she says the are perfectly fine. Umm no they are no I almost wrecked thank god I didn't