Google Console Keysign Mis-match

Not your usual mis-match, howerver. every time i try to upload my .abb i get get message:

"Your Android App Bundle is signed with the wrong key. Ensure that your App Bundle is signed with the correct signing key and try again. Your App Bundle is expected to be signed with the certificate with fingerprint"

So Google expects the B6 Key, I'm assuming the origanal one, which i don't have, find, and all this time Ive been using a B4 Key. which I think is from, stamped from Android Studio's kind of "throw away"-practice key , which is the B4. So see where Im coming from? & real key has never been used.,The last guy also said i had to replace the data inside my gradle dot someto possibly. IDK.. Pls, try to help me out, This is my "just for fun dream app, Im also a cancer patient(i'll send u proof if u want me to, I can't afford much, Pls, tell me one section at a time, I'll go and do it, then I'll return, and we do it this pattern again, I say this way if it's ok?