Please post in the correct category next time. You can install core protect to prevent add a few tools to detect and rollback griefing. you could install a plugin like grief prevention to allow people to claim land.
It is a premium plugin that does look cool...
https://www.spigotmc.org/resources/lands-land-claim-plugin-grief-prevention-features-gui-land-protection-management-1-13-1-14-ready.53313