Hi,
Since demolition and structural changes (removing windows, raising lintel, new exterior facade, new interior plaster, etc.) are certainly out of the question,
why should that be out of the question? If the windows were correctly shown in the construction plans, they will first deliver exactly that. Done.
If the site manager notices this too late, the additional costs are their problem, not yours.
The timeline will become problematic, this is a bigger operation that will certainly delay the move-in by several weeks.
If you are under time pressure and the construction company knows that, they will try to play for time.
If you want to agree on financial compensation: consider how high the reimbursement would have to be for you to be happy with it for the next 40 years.
€500 compensation is quickly forgotten; you will be looking at the windows that are too low for the rest of your life.
Best regards,
Andreas