Freecad is a parametric modeller, unlike Sketchup's approach. A totally different (and incompatible) workflow. Working through Joko's tutorial will help.

https://www.youtube.com/watch?v=Odr5viqPwkc

A beginner's overview and tutorial from Joko Engineering:
https://www.youtube.com/watch?v=Odr5viqPwkc

Others that he's done:
https://www.google.com/search?client=fi ... ko+freecad

And by more info, PLEASE READ the pink banner above your first post.

This might help. I'm using Windows but I suspect that a second Linux window will do the same.
I switched to (or opened) a second Window/Screen (Winkey-Tab on Windows) and started up a new instance of Freecad. I could open a new file there without corrupting the first Window/file.

Just posted a couple days ago:
https://www.youtube.com/watch?v=Odr5viqPwkc

Translation... Good morning all, I would like to know if anyone has any idea to solve this problem I am facing. To familiarize myself as well as possible with Freecad, I will look for technical drawings quoted on the internet and I realize them with Freecad. Often I have to glue a reinforcing rib wh...