Realistic construction time for a bungalow?

Well, then bring it on!
(where there is a specific plot of land, you can also investigate its development plan or similar).

Translation for laymen:

Share information about your property (municipality, parcel, etc...) then 11ant would gladly show you what you are allowed to do there and what not.

I would now also say that you might possibly be faster with a local bricklayer or carpenter general contractor who is well networked locally and has a good connection to the building authority. With a prefabricated house general contractor who, if in doubt, operates regionally, you are just a number among many. You will still see the local master at Kaufland for the next few years.

Depending on the development of the material situation, it can also be significantly more.

Rrrüschdüsch: the bottleneck at the moment (and for several months already) is the delivery times of the heat pumps, for example; during that time, a dozen shell constructions have been erected (and dried).

Translation for laymen: Share information about your property (municipality, plot, etc...) then 11ant would gladly show you what you are allowed to do there and what not.

Note well, without links! - so development plan number/name, municipality; possible encumbrances, status of the property ...

Then it depends on whether you are building with a general contractor (GU) or a prefabricated house provider. The GU was much faster to realize for us; with all prefabricated house providers, we wouldn’t have built last year anymore,

The prefabricated house provider is also a GU/general contractor. By prefabricated house provider you probably mean the GU building in timber frame construction. On the topic: We are currently building with a GU in solid construction. About 14 months ago, we were where you are now. After 3 months, the GU and suitable floor plan were found, 2 weeks revocation period after GU contract (nothing happened), after another 2 months the building application was ready, the following 3 months the building authority took for approval, 1 month needed for preparatory measures such as excavating the building pit and creating the base. Since then, and for the following 10 months, the GU is up. After that, there still won’t be a move-in. Beforehand, flooring, walls, and ceilings have to be done by ourselves. Two more months are planned. In total, we hopefully will end up at about 22 months. From the first planning to moving in.

May I briefly add to the question? Similar situation: Apart from the property with existing buildings (incl. development plan), nothing else is present yet. Can I infer from the above list that the first 9-10 months are for formalities and planning before the excavator comes for the demolition? Do seasonal weather conditions need to be taken into account? Foundation slab in winter?

Answering the question so generally is really difficult, especially if you are not really in the planning phase yet. At the beginning, we had many conversations with different companies and after about 4 months we decided on one. We started the conversations in March 2021 and the first excavator rolled in July 2022, currently the shell is standing, the roof and windows are sealed, installations are done, the electrician is finishing today and in the new year the interior plastering will start right away and then the screed. Roughly, one could say that two years after the first conversations, the interior work begins/has started.

However, we also planned completely individually and did not stress ourselves, neither with the selection of the company nor with the house planning.