Hallway wood floor maintenance

I've got a 1930's house with the original (I assume) wooden floor through the hallway. It clearly hasn't had any maintenance for years before we bought it and needs some tlc, so am keen to look after it better to keep it in the best condition it can be. I want to avoid sanding it back as I like the character, just want to give it a good scrub down, protect it with a coat of something and refill the gaps - it looks like very old wood filler has been used so just want to refill. What would be best? Pics attached.

Thanks

Steve

Sanding it would be best, even if lightly by hand, after which you can varnish wax or oil it.

The sawdust from sanding can be used as filler.

Blup