Protect windows during the construction phase, but how?

do you mean the protective films from the plasterer or others?

The cleaner glued plastic sheets to the frame, I don't even know exactly what kind they were - that was summer '18, it was 38°C and I made sure not to stay in the house because of the humidity... I really felt sorry for them, but they did a great job. In any case, he removed them again afterwards, so I can't say exactly how thick they were.

Our windows and patio doors were also wrapped in foil from installation - it was only removed two weeks before the final inspection. We had no damages.

We will protect the windows and frames with glass protective film. However, it does not offer significant protection against mechanical impacts.

We will protect the windows and frames with protective glass film. However, it does not offer much protection against mechanical impact.

Rick, can you recommend a specific product?
Thanks!

Google simple self-adhesive glass screen protector. Use a branded product. I've heard stories where the printing has rubbed off... But it does not provide protection against severe mechanical impact.