greetings, I am planinng on refinishing my floors myself. My problem is that the previous owners put vinyl tile over the hardwood floors. I peeled off the tile, but the glue is a mess. Can i sand the floor with 20 grit to get the glue off or do I have to take the glue off before sanding. What is the best way to get the glue off? Is there a machine that i can rent to get rid of the glue? Thanks in advance for your help.

Go ahead and use the 20 grit. The wheels on your sander will need to be cleaned (mineral spirits and a scraper/putty knife) before you continue with further sanding cuts.

maybe put masking tape on the wheels to protect them on the first cut?