Can I get rich if I find objects under the ground that are from the Roman or the Osnian Empire?

I have been watching the Film Protector in Netflix for a few days now and am now fully interested in Middle Ages. I would like to search for valuable objects from the Roman and Ottoman Empire.

Can I recover valuables from the earth with detectors and then sell them?

For example, if I outsource such a valuable sword or dagger and sell it, can I count on € 1m or?

Do you have to give everything and that's a good thing.

Depends on where you find them. In most states you have to give found treasures.

https://www.faz.net/aktuell/wirtschaft/recht-steuern/kniffelige-rechtslage-vom-unglueck-einen-schatz-zu-finden-12166.html

For example, if I hid such a valuable sword or dagger and sell it

You will not be allowed to sell it, but you must inform the nearest available archaeologist - for example, about the city or a museum, the university, etc. You do not acquire sole ownership of valuable finds. Look in the monument protection law of your state.