help please :(

hi guys i don’t know if this is the right place to post. But i’ve been having a 1997 E36 318i for a couple months and today I noticed that a fan of some kind is running really really loudly while my car is shut off and was notified that it could kill my battery. now i do not know anything about cars (i am a girl), so i just searched up the problem and kept reading about it but all the answers varied. if anyone has gone through this issue and fixed it or if you have any idea what it could be any help would be appreciated!!! i would also really appreciate if someone had like a map of some kind of anatomy for the stuff that’s under the hood ?