Here is how you transfer the ownership and all rights on a map to someone else:
1. Open the map.
2. Click on “Share”, then write your team members email-address, and click on "send invitation"
3. In the same window, set the permission level to "admin".
4. After setting the admin permission, scroll down and choose "Transfer ownership". Type in the person's username and click "yes" to confirm. Now you have transferred the ownership of the map.