Geometry checker not removing overlap between features

How do I remove overlapping polygons in QGIS?

You can use the ‘Check Geometries’ plugin (Vector/Geometry Tools/Check Geometries) to remove overlapping areas. Save this answer.
 

How do I fix geometry in QGIS?

QGIS comes with a built-in algorithm to fix geometry errors automatically. Search for and locate the Vector geometry ‣ Fix geometries algorithm. Double-click to run it.
 

How do I fix self intersections in QGIS?

Quote from video: The first step to solving this problem is to go and find where it's actually invalid. So the first place we go is up to our vector tools into geometry. And we have to check the validity of the land.