House purchase - Experiences with open bidding process?

It is a detached single-family house.

Set a boundary, drive there, participate up to the limit, have the financing confirmation ready. If you come off worse, then so be it. There are worse things than not buying a (too expensive?) house.

Is this even being done live?

No, not live. Each interested party has the opportunity to submit a written offer by a specified deadline.

We have now experienced this a few times. For house 1, we immediately said that we would not go above the asking price. The realtor said he was expecting a 10% premium (should have cost 259). House two was listed for 185k, clearly in need of renovation (we had estimated 85 to 100k). It sold for 265. The last house was a private sale with 17 interested parties. It was listed for 240, we went up to 292, and it then went to someone else for 295. If the location hadn’t been so borderline, we probably would have gone to 300 because otherwise everything fit. Now someone else is happy with it. You have to set a limit in any case.

We already thought during the viewing,

But you are only „briefly“ with the agent. The exposé is „waterproof“? If you know how much still needs to be renovated (10k€, 50k€, 100k€) and how much comparable properties cost, you can clearly set the limit. 250k€+„bidding euros+ purchase costs you will definitely end up at 300k€. + renovation. Heated with? Rating F,G,H…?