This guy you had work on your tiles kinda sold you a bill of goods.
If the tiles are cupped or saucered or concaved it is likely they have been that way since they were originally installed. You probably have "green marble" which has nothing to do with the color. Green marble is moisture sensitive and will curl slightly if the wrong adhesive is used to install them.
All is not lost but you need to find a professional "restoration expert", not some guy with a rented buffer.
Your marble must first be honed (re-honed) to eliminate the curling. This can easily be done with the right equipment. Then and only then will the marble be plane enough to polish properly. Polishing takes a series of pads and pumices and polishes to do it properly.
I would never use a garden variety floor wax on marble I think that is some novice and bad advice.
Once you do that you have created an ongoing maintenance issue and the only way to keep the floor looking nice would then be to strip it of the old wax from time to time and that is a very bad idea with marble. Strippers can ruin the stone.