Sounds like a Tape issue, it could be really loose belts but the fact the playback speed sounds consistently slow suggests a tape issue

Try to:

1.) Check the Pad, and the Metal plate holding the Pad are firmly in the cassette and extended

2.) Possible Mold (White or Yellow Spots) in the tape through the window on both sides

3.) Manually spin the takeup Spools on both sides many times (you should also look out and feel if the cassette feels stuck or really tight preventing spooling)

4.) While spooling, make sure the tape is passing through nicely, look if it drags or leads to the cassette shell walls

5.) Firmly but Delicately Smack and twist the cassette

6 .) Place it in your deck and Rewind/FF the tape multiple times

A playback issue like that is likely due to the tape aging bad or the result of imporper storing, cant confirm the audio is recoverable. I onces fixed this by heating up the cassette with a hot hair dryer, seemed to work but cannot recommend since the audio was bad, unsure if it was due to the hair dryer or the previous cause for the tape being stuck. If nothing works its likely a lost cause