The best way to remove paint from concrete is with a pressure washer if you have one. You can also use a wire brush and latex paint remover, and rinse...
The best way to remove primer depends on what kind of primer was used. There are different kinds of paint primer remover. For concrete, you can use chemical solvents such...
You’ll need to clean the floor thoroughly and patch up any holes, then apply a water-based primer. If you like, you can paint on a base layer of some type...
You may be able to use some lacquer thinner and scrub it off. You can rent a pressure washer, which generally has good results, or maybe try and sand it...