Breech of contract

My business partner accused me of stealing money from the safe. Banned me from the business and decided I was a silent partner without my consent. Refused to apologise for the unproven and upsetting allegations. I want to sell my shares of the company back to them. I paid 800,000k and they will only pay 350,000k I have another buyer but he doesn't seem interested. Can you help me get any of my investments back? Sue him for slander and breach of contract?