ᐅ Protecting Natural Stone on Balconies

Hi everyone,
we have bought a new apartment.
There are natural stones on the balcony (in my opinion), and you can see every stain that is difficult to remove.
How can I protect them and apply some kind of protective coating so that they are easier to clean?

What do you mean by natural stone? Those are concrete slabs. Normally, they should have some kind of impregnation from the factory. It can also be applied afterward, but of course, how effective that will be is questionable. Go to the home improvement store you trust.