Do you have any examples of how to make a pull up bar? Sounds like it could be rather painful if you get it wrong
Length of bar the same width as your door frame. Depending on the door frame and your weight this could be anything from an old broom handle to a bit of scaffold pipe.
Offcuts of sheet wood (ply, mdf, pine, whatever)
Hole saw the same size as the bar (or a coping saw, or a hacksaw at a pinch).
Cut bar to fit door, cut 2 rectangles of wood that fit neatly in the frame, about 10cm x 5cm. And make a hole in them that’ll take the pole (if tools are limited, cut a V notch into the top, and hang the bar from that, and put a screw into the doorframe above the bar to stop it jumping out.
Or for less faff, you can get them for £12 on ebay.