How to make the same thickness of the roof in several places? I don't want to change angles of edges to 90 degrees to measure it, I wanna keep edges with existing angles. Help me, please.
You could try to extrude with the Shrink/Fatten mode: Select your mesh, press altE, choose the Along Normals mode, drag the extrusion, then in the last operation box (bottom left) enable Offset Even.
(You could also use a Solidify modifier, in this case, enable its Even Thickness option)