Hello and welcome to OSM.
Thanks for adding houses but I think there is a problem here.
The software reports that you are tracing buildings on top of… aerial imagery.
This is not how we work.
If you do this, you will not be tracing the correct shapes.  Aerial imagery is taken by aircrafts but every house is slightly distorted, and those pictures change every year, and the houses look a bit different with every release.
In Flanders, you should use "Digitaal Vlaanderen GRB" and draw on top of that.  Those are the official shapes of buildings.
In the online editor you will find this under the Background button (right-hand side of your screen).  Scroll down the list until you find the correct background.
Hope this helps.
Happy mapping.