Cost to renovate a complete house

I would reconsider the full commissioning as well. Especially in existing buildings, architects are usually quite expensive due to the remodeling surcharge, but they typically provide comparatively little service because, for example, the entire building services (electrical, water/sewage, heating, controlled residential ventilation, etc.) are only "taken into account" (i.e. drawn in the plan) by them, but not planned or supervised. And although the "construction fabric to be processed" is usually factored into the fee, I have rarely heard of an architect worrying about things like basement waterproofing if no specific measures are planned in that regard.

You are also not planning any major remodeling work (such as an extension or similar), so the "design part" largely does not apply, and since it is not exactly a run-down property, I would not expect any significant "unpleasant surprises" that an "ordinary" craftsman would be overwhelmed by in the end. For trades like windows, screed, parquet, in my opinion, you can rather afford a corresponding expert who takes a look at these points selectively. It is better to invest a bit more in execution and enjoy how accurately well-paid and motivated craftsmen get to work.

Unfortunately, I just don't know who I should contact with our renovation plans. Architecturally, there really isn't much that needs to be planned. What he can do, however, is handle the tenders. That sounds reasonable to me. As a layperson, I find it difficult to find the right craftsmen, to assess/compare the services, and above all to coordinate everything. An alternative for us would be a general contractor (is it called that for renovations as well?), who would take on (almost) all trades and plan with us.

You don’t need tenders. You just let all the craftsmen come, discuss your ideas on site, and you receive offers. They can also tell you what makes sense, how to save costs, and advise you.

Otherwise, they only blindly fulfill the tender criteria, no matter what it costs. The architect doesn’t care about your budget either. He gets three offers, no matter how expensive they are, and makes you sign. He has no interest in saving costs. You can also see that in his 65k invoice.

Brief interjection: The current floor structure is 6cm, how much of that is screed and how much is parquet, laminate, or similar?

Edit: The question should have gone in the other thread, I have reposted it there.

An alternative for us would be a general contractor (is it still called that in renovations?), who takes over (almost) all trades and plans with us.

I would have no qualms calling them that as well – however, only a few builders are equally skilled in new construction and renovation, even though market players like to believe otherwise. At least that is somewhat more often true than with architects (the young ones are usually only good for new builds).

Unfortunately, I just don’t know who to turn to with our renovation plans.

Either a (operating nationwide) genuine general contractor (there are also some who specialize in old building renovations), or you take, for example, a local, renowned heating/ventilation-sanitary company (majority of the contract sum) and have them bring in their "partner companies" for the other trades. We have at least had very good experiences with the second option. The people get along well, push each other because everyone measures themselves by the (good) work of the other, and above all, they actually communicate without the "construction manager" having to call a meeting every time.

And maybe just fundamentally: With a fee of €65,000 (excluding planning and supervision of building services), you can easily consider sending one of you into part-time or even unpaid leave during the construction phase and taking care of it yourself. You don’t need to know dozens of DIN standards by heart to save huge amounts of money on construction through "supervision." I would argue that 85% of all problems on construction sites are based on misunderstandings and/or unclear instructions, and the client with a plan in mind can prevent that just as easily as the highly paid architect.