I’ve tried several ways to draw the green part of this picture (the walls) but any of them ended as I expected.
The problem is the thickness, I don’t know how to do it and keep the angles constraint.
Could someone give me some advice? or tell me if there is a similar tutorial.
This is one of the ways I tried, but I did it in several ways, doing the 3D without thickness and then copy, scaling and paste in place, but any of them worked.
There are many ways to get to the point shown in your screen shot. When you get to the point at the end of your GIF, you could just select the inner edge of the wall and move it straight up to intersect with the angled edge.