Thx the video helped a lot i now have rooms to the correct dimension and with the automatic dimension feture i have correct measurements also for most furniture like doors/ windows
the video also answers to a large extend my other questions about joining walls

However Iḿ in dire need of a method to create accurate measurements that cannot be automatically generated like in the video, using the mouse it the pointer jumps 3-7 mm (at maximum zoom while still workable) and I cannot use the enter key to edit the measurement from the keyboard

cannot insert image - sorry