After a question i will post here that the oven entrance is:
Corten steel but you can use whatever steel i guess.
The measurments are 8 or 10mm thickness.
The actual entrence is 160mm Deep. If i were to make a new i would make it 100mm to make it even more easy get into the oven.
I made the curve of the flatsteel 80x8mm with a machine that my firend has. You need to go to a steel mechanical workplace.
I welded these two 80mm togeather to get my 160mm Deep.
Alternative number 2 is to leave drawing at some workplace and get it done. Costful, yes probably.