For each map it is recorded which user made which changes. In the so-called “Map History” you can view all changes and see who has contributed to your map.

To view the map history, go in edit mode and click on the three dots in the top right corner. Then select “Map History” from the dropdown. A page will open that looks like this:

The individual entries are linked so that you can open each changed element directly.

By clicking on the time icon you can open the revision history for each box.

If you want to delete the entire history, click on the "Delete entire History" button at the top right.