House purchase - Experiences with open bidding process?

Well, whether the losing bidders are informed of the highest bid and then allowed to increase their bids again, or if there is only one round.

We also once looked at a house that was being sold through a bidding process by the real estate agent. The house was from 1972 and was completely in need of renovation. It had been vacant for 5 years, presumably unheated. The minimum bid was 229k, which was almost the limit for us. We had considered bidding 237k and also estimated renovation costs of 150k to 200k. We did not place a bid because at almost the same time we also looked at our current house and hoped to get it, which fortunately worked out. By chance, we then found out that the house was sold for 286k in the bidding process.

does not offer 5k more but 6k, [...], that one k can make the difference

No, then rather 5,100 or if the step size is not specified also 5,013

There is no general answer. It's like with Exxx, 1,2,3 mine. If it is supposed to be the house, consider whether to give away 270k somewhere.

The problem with eBay is of course that you definitely pay the offered price - not the minimum more than the second highest bid. ;)

Who tells you that there are several bidders? That could also be a lie from the broker. Have you seen them?