How long does it approximately take from the start of planning until approval?

Sixty-three.
Seriously:
You have the planning duration under control yourself.
You have the preparation of documents for the building application under control yourself.
Building permit varies between 2 and 10 weeks depending on the municipality. This can be easily inquired about.

Property purchased in October 2019, plans roughly created, offer obtained (We had already been to companies before and knew whom we would choose for the construction) in December to the architect. By the time everything for the building application was completed and clarified, it was February. Building application submitted and building permit received in April. Construction will start next week. Many building authorities need, for example, 6 months or more for the approval. Hope this helps you a little further.

It can also go faster with a lot of luck... Got the plot in June, planning until October because the architect from the general contractor was a bit slow and we kept wanting many changes to the floor plan ourselves, November signing, March start of construction, currently it looks like readiness for occupancy in August. Completely normal solid construction turnkey without a basement. Normal case? Rather not, judging by what you hear.

Thank you for the timeline. We just want to know approximately how long one has to plan for it.

Have you already read it?

With us (municipal property): 02/2018 Commitment for the plot 03/20 03/2018 Start of development 12/2018 Completion of the road 12/2018 Submission of documents (exempt from approval) 02/2019 Start of construction 09/2019 Move-in The plot was ready to go from January but could only start once the boundary stones had been set.

With us (municipal property):
02/2018 Commitment for property
03/20
03/2018 Start of development
12/2018 Completion of the road
12/2018 Submission of documents (permit-free)
02/2019 Start of construction work
09/2019 Move-in

The builder was ready to go from January but could only start once the boundary stones had been set.

A question: in the end, did you do the flooring and painting yourselves or have it done?
We start construction Wednesday and are really hoping to move in before Christmas. We are doing flooring and painting ourselves.