Hello,
Yes, it is much better when tracing from GRB. I understand it must be difficult to do it in the online editor, because tracing accurately requires a lot of zooming in and out.  I did a few more fixes.

I am worried that many buildings are still missing in this area.  There is an ongoing effort to automatically import government data into OSM, which might help to speed things up here.
https://wiki.openstreetmap.org/wiki/WikiProject_Belgium/Building_and_address_import/AIV_GRB_building_import/Import_plan