Snap-to-grid turned off
Reading help about drawing walls should give you some hints about using tooltips and magnetism.
This looks like this bug. Relaunch program installer and choose 64 bit architecture when prompted.
I would suggest to use "supprimer" rather than "ôter" which I never saw in a program.
Et en installant la version 32 bit?
Level Tags Manager plugin
By the way, the paid Microsoft pop up isn't a bug.
Try the free version available at https://sourceforge.net/projects/sweethome3d/files/SweetHome3D/SweetHome3D-7.5/SweetHome3D-7.5-windows.exe/download and if it still doesn´t work, describe your problem.