Can you paint over bathroom paneling? Help it’s over 25 yrs old

yes. You will want to prep it really well. You can wash it down with TSP or you can lightly sand it. Use a fine sandpaper if you choose to sand it as it will be a smoother surface to paint. Since it's in a bathroom you'll want to use a semi gloss paint.

Matt or Satin Emulsion.

Make sure you clean it well, and let it dry completely. Sand out any scratches or imperfections. Clean sanding remains off and let dry. Put a good coat of primer on then paint with semi-gloss or satin (for a less glossy look). Let dry good before you shower.

Yes, wash it down with TSP (trisodium phosphate). Then use a good stain blocking primer like Zinsser 123, BIN, or Kilz. Then use a bathroom paint. It has a mildewcide in it. If the paneling has grooves in it you can fill the grooves with drywall patching compound. Let it dry overnight. Next day use a damp sponge to smooth out the compound. Prime and paint.

You can! Clean first very well ( TSP)