Doors and frames from different shops?

The problem is that shipping costs apply if I stay under €500, so I would prefer to order everything at once. But I will measure the walls exactly again tomorrow.

Exactly, hold a 2m straightedge against it and report back.

Ok, I'll just measure again tomorrow. However, I suspect it will come down to the smaller frame. Thank you

But keep in mind that you then have no reserves. Maybe 50/50 is an alternative?

What exactly do you mean by 50/50?

I tried to find out a little. According to the homepage, the frame has a wall thickness compensation of -5 / +15 mm. Then I should always be correct with the smaller frame if it can still be adjusted within the above-mentioned dimensions, or am I misinterpreting this?

Measured again today. They are actually pretty much 65mm everywhere, possibly 66mm in some places where there is still wallpaper on it.