Window damaged and roof overhang

Yes exactly, the contract says approximately 20cm. When the plaster is applied, about 2 cm, then I am at 16cm instead of 18cm. I also added a photo of the window, a bit further away. One is 2mm and the other next to it is 1mm.

Are there special pens for touch-ups?

Don't worry about pens or exactly how to fix such errors, that's not your problem. I would report the defect in writing. More flaws might appear before the final acceptance of your house – the billing is done at the end. In the end, if I were you, I would insist on repairs and if they are not done to your satisfaction, an appropriate amount will simply be withheld from the final invoice :)