Hello, and welcome to OSM.

It looks like you have inadvertently been tracing buildings on aerial imagery.

Those images are not suitable for buildings, they will show a distorted view.  Can you please redo your edit and trace on the appropriate base layer,

I see you are using the online iD editor.  When you are editing, on the right side of your screen, there is a "Background" button, where you can scroll down to "Digitaal Vlaanderen GRB".  Please make sure to only use that one when touching building shapes.