To remove JoomProject entirely and properly from your site, go to:
Joomla Backend -> Extensions -> Extensions Manager
From there, go to Manage and filter the list by type Package. There you should see the package called "JoomProject Project Management System". Removing this package will remove every extension that originally came with it, including all the JoomProject database tables that were created.
Removing single JoomProject extensions is not recommended as it will lead to instability in the remaining extensions which might depend on the ones you've removed. If you dont want to use a particular extension, disable it instead so that the code is still there and the rest of the system can operate normally.