Why do my new car brakes creak/squeak?

Pardon all my car questions but I am really just trying to learn more about cars because I am a young female and I do not want to get ripped off again at auto places anymore.
Anyways.

So about a month ago I had new front brake pads (ceramic) and new rotors installed on my car. For a couple weeks now when I am coming to a complete stop my front brakes (drivers side especially) creak as I’m almost stopped. (ESPECIALLY downhill but not always it can be on a flat surface as well just less loud) They only “squeak” however when I do a super hard stop. I am concerned mostly on the “creaking” The creak only happens when my brakes are cold. If my car has been running for awhile my brakes no longer make any sound. (no creaks nothing) I had this checked out by the place that did my breaks they said they couldn’t hear it (yeah because my car was warmed up) but they took my brakes apart and inspected them and found no problems so they re-lubed my drivers side and off I went. Well it still makes this sound, and as far as I’m concerned brakes aren’t supposed to make any sound. They tell me its fine but I really don’t want to be damaging another component if its not fine. What do you guys think it could be?
Also as a side question my lower ball joint on my drivers side the boot is ripped but the ball joint still functions fine (my wheel turns fine no bad symptoms etc) what do you think about that? They also told me the ball joint was fine with the boot ripped. Just looking for opinions. Thanks!