First of all, a big thank you for all the further answers/questions. Unfortunately, I did not receive any push notifications that there were additional comments. I still have to check where I can set that up.
In the meantime, I have decided on a change and now need to secure myself to ensure that this does not lead to any additional costs, for example due to construction delays, so that the costs quoted to me for installation, windows, and security roller shutters shall apply. I now have to document this in writing and hope that I think of everything.
Also, is there a professional closing that I can add to the letter, such as asking the developer to please inform me if other/further costs and/or contract changes may arise that I have overlooked?
I will just check the forum from time to time today to see if anyone has a better formulation for that.
Wishing everyone a great Tuesday.
Many thanks,
Sophie