How can I remove the manage by a company from my chromebook samsung

Are you set as a local administrator? If not, then go to your IT department and have them add you to the local administer group. Some restrictions are set by group policy, if you need to do something and you get a message stating that group policy is set to prevent your actions, then go to your IT department. If this is an enterprise version OS and your company has set group policies then trying to go around the policies may cause problems in the company enterprise and may have strong disciplinary actions that follow.

If you bought this computer second hand then you should reinstall the operating system after formatting the hard drive.