“Can you get rid of bad breath if you have periodontal disease?”

Yes if the periodontal disease is treated and a healthy oral hygiene condition is maintained, that is including to brush the top of the tongue to remove bacterial plaque and dead skin cell that will appear on a tongue scraper. If this doesn’t solve the problem then there may be further gastric issues to address but typically not.

Usually when you get your periodontal disease treated, the bad breath due to periodontal disease should go away.
Please see minimally invasive periodontal treatment option:
https://youtu.be/mo6MD69DUZI