Construction costs realistically estimated?

I would definitely clarify the issue with the "window switch" with your responsible district chimney sweep. It's a tedious topic.... Of course, you play it safe with a recirculation hood, then you don’t need a pressure switch, window switch, or "open window" with a DIBT-approved heating fireplace.

Thank you very much for the initial assessment ... then we can confidently go to the contractor.

.. and why don’t you go to an architect and have the appropriate plans made ... as a business consultant (that’s how it says for you) you should be able to properly plan such a "business" ...

.. and why don't you go to an architect and have the appropriate plans drawn up ... as a business consultant (that's what it says for you) you should be able to properly plan such a "business" ...

If I say I go to the contractor, does that exclude involving an architect?

... as a business consultant (that's what it says for you) you should be able to properly plan such a "business" ...

That's what I've been waiting for

If I say I’m going to the contractor, does that exclude involving an architect?

if the architect was commissioned by you and is therefore independent of the contractor, then it would be an advantage for you, but then I wonder why the architect is not able to determine the areas, square meters, quantities, and so on, for you and obtain appropriate offers, now the business consultant is asked whether he planned this correctly ops:

Is the project realistic with a "good" equipment?!

.. no one can reasonably answer that for you, no one knows the plans, simple or complicated? no one knows the actual planned items to be installed, for example: you can get a good car for a good cheap price, the same car you can also get for an exponentially higher price if your desired extras are added .... but no one knows these extras in your construction and the location of the building plot is also decisive, reaching a small town on the edge of a development area is quick and easy and reaching a building plot in a big city in an upscale villa district takes considerably more time and this time will also be charged to you by a contractor if he has a good business consultant who advises him properly

Thank you very much for your assessment.