When I have an issue with a CD, step one is furniture polish, which both cleans it and fills in scratches. If that doesn't do it, step two is to polish it with toothpaste, then clean it with furniture polish. https://www.wikihow.com/Repair-a-CD-With-Toothpaste

Sadly not all CD- / DVD-drives are made equal. My benchmark is an old, fairly banged up CD that has the game music as regular audio tracks. I've noticed a particular track will skip or elicit other weirdness when a weaker CD-drive is used. A better quality drive will play the audio without issues. Repo Man11's suggestions are all good, but also try with a different drive.

I repaired a lot of bad PS2 dvd's with Brasso with mostly good results.
The process is to have a flat surface to put the cd/dvd on, have a fine clean cotton cloth and dampen it with a bit of water, shake the bottle of Brasso, put a little bit but not too squeemish and start rubbing, add a bit of water and/or Brasso if needed.
The amount of polishing needed depends on how badly damaged the cd/dvd is.
Once you're done clean the cd/dvd with a clean cloth or microfibre cloth and spray it with a bit of silicon oil.
With a bit of luck the cd/dvd should work although also take into account the drive may not be good anymore and can either need calibration or a laser replacement.

I've tried the toothpaste method but it never worked for me.
There is also a polishing agent called Commandant which might even be better but I've never tried it.