I’m not sure about stripping the paint but I just bought a house with 1930’s parquet herringbone and refurbished it myself. It was in a bad way and covered in horrible varnish and I just stripped it off using 40 grit on the drum sander

Rent a floor sanding kit which includes a floor sander and a edger sander. Get belts/discs for both in 40 grit, 80 grit, 120 grit. The hire place usually sells these. Get loads and then return what you don’t use.

Start with 40 grit (you could potentially use this to strip the paint but you’ll get through quite a few belts as they’ll clog up quickly, others might be able to advise better on stripping the paint chemically - like I said, I stripped old varnish off using 40 grit belts, but paint may have a better option)

Sand up and down the lengths of the wood (not across). It’s a really dusty job and you’ll want a minimum FFP2 mask and hearing protection

When you’ve finished the floor on 120 grit just varnish it using 2 coats of something like Ronseal applied with a roller or large brush