So here is the story how I converted the agfa clack into a pinhole.
First take of the our ring and the lenscover thingy. The ring is attached with one screw on the bottom. The lenscover thingy you can twist of.
After that take out the lens after unscrewing the screw that holds it together.
Next you unscrew these screws:
The shutterpane will dangle loose and underneath you can add a pinhole with the help of a little glue:
Put it back together et voila you've got yourself a pinhole camera. It is that simple and you don't need, like I did, to take the complete camera apart. It is interesting but not necessary. You might want to make sure of the perfect round circle and that the pinhole is completely centered. However I didn't do that.
Regards,
Peter