Renovation costs mid-terrace house built in 1995 - and consultation

I completely disagree here.
Remove all tiles.
With a decent chipping hammer, this can be done by two people in a few days.
I would also completely redo the bathroom. Sure, it is usable, but you won’t feel comfortable in it.
Also here --> do all demolition work yourself.
When ordering containers, pay attention to sorting purity, meaning do not mix construction debris with residual waste.
Then it counts as recyclable material and disposal costs are quite low.
25,000€ for 160m² of floors is, in my opinion, too much; if you prepare everything yourself, it can be done much cheaper.
I consider painting costs realistic if nothing major is changed on the surfaces otherwise.

Yes, if you can do it yourself, okay=). But if not, would it still be worth the money to do it?

Even if you have it done, it doesn’t cost the world. Anyone with two arms and a hammer can do that. You really can’t do much wrong with it.

It would already help me if I knew whether the 10 euros per sqm for chipping out would be enough (that was the expert's assessment). At 38 sqm (if I only do the ground floor), it would be worth it to me. Doing it myself is probably difficult for me to manage time-wise.

What would be the disadvantage if you don't remove it? So what speaks in favor of such an expenditure of money, what is better afterwards? And if you chip out the tiles, can you get the floor leveled again without much effort?

What scares me a little about a plan like Zwischenhaus is whether in a few years you will still get the same value for the house, in other words, whether prices will rather go down.

That can never be completely ruled out - but it is a phenomenon that would affect the market in your area less strongly than the national average. I wouldn’t advise you to go for Zwischenhaus if I thought it was a matter of only a few months until you reached your (stage) goal elsewhere.

What do you think, how much can you actually negotiate? The appraiser created a traffic light for me from green=500k through yellow (520) to red=550, which he would see as an absolute upper limit. However, the house is listed at just under 600. I once offered the broker 560k and he said he would include that in the negotiation. Based on the appraisal, I would try 540k though.

Your appraiser’s perspective is not only his own – the banks of your competitors share this view. If a property is not worth the seller’s desired price as collateral, financing willingness cracks and the number of your competitors dwindles. You will have to learn to bluff, or you will pay extra. That means: if the value according to the appraisal is well-founded – and I see the “traffic light” alone as an indication supporting this assumption – then you should confidently orient yourself on this value. You may have to let overpriced properties go. I understand that you will think I can easily talk because it’s not about my sausage, and that consequently you will not offer the value, but “the value plus x.” That is also fine, you just shouldn’t offer value plus two x or plus three x. I think I should offer coaching or training in this area (“Arm wrestling with brokers” *LOL*).