Welcome to the community
If you are the owner of the collection, you should be able to edit/delete the collection. If you are still unable to do so, could you try to sign out and sign-in and see if that helps?
Additionally, check if you are on the latest version of the application (Settings > Update).
Regarding your queries:
- The permissions are divided across as Team, Workspace and collections. Permissions to collections wouldn’t be derived from Teams and they are distinguished as per the workflow. This document on RBAC would provide a clear explanation of this.
- To prevent others from making changes to your collections, you will need to provide “Viewer” access to users in the workspace and this feature is available only on paid plans such as Business and Enterprise. The option “Control access, roles, and permissions” on the pricing page confirms this.
Hope this clarifies : )