A potential lawsuit against my construction project is looming! What now?

I purchased a plot of land through a property developer, designated as building land in this case. [...] Before there is a building permit, as far as I know, a building preliminary decision (preliminary stage to the permit) was made, which was positively approved by the authority (responsible building department). However, the office failed to inform the neighbors (about the preliminary building decision), who would have had a 4-week deadline to revoke/file a lawsuit. Due to the office's failure, the 4 weeks have now become 1 year!

First of all, it’s not your problem; the office must inform the neighbors. A building application must be submitted anyway if only a preliminary inquiry has been made so far. The neighbors can then object if it deviates from the development plan. If the building application goes through, the preliminary inquiry becomes irrelevant anyway...

Is there a development plan? Was the plot not previously designated as building land? Why are the neighbors involved at all?

Or could the neighbors be successful with an objection? As long as all the rules are followed in my construction project, I would not worry...

Exactly. They could even challenge the building permit later if, as mentioned, there are deviations. There is a development plan and it was also approved by the building authority. We will more than consistently adhere to the requirements such as minimum distances so that no trouble arises afterward. As far as I know, even the immediate neighbors must be informed or instructed by the building authority. This was simply neglected; additionally, I have also found out that both the preliminary building permit and the building permit can be challenged, but only if there are valid reasons, such as incorrect construction methods or similar. In other words, deviation from the development plan. None of this applies here. I am very curious about what the hardware store will tell me on Friday. And last but not least, no lawsuit was filed. Oh, the neighbors did find out since the building plot was constructed and surveyed, but also, of course, through hearsay. Ultimately, probably by inquiring at the building authority itself.

The developer produces this, I sign it and submit it to the building authority.

Then it is not a Bauträger.

An I think about it is, as already said, somehow ridiculous.

But permissible until the deadline expires.

Then it is not a constructioncarrier. But permissible until the deadline expires.

That is correct. It is permissible. But it must be in writing and a justification must be provided that is valid. A "I don't want it because it looks stupid" or "I don't like my neighbor" obviously doesn't work that easily. Also, as the plaintiff, you must be aware that if it goes to court, it can become expensive. But fortunately, that is not the topic now. Rather, it is about the legal situation and what happens when the building application is submitted, how the building authority reacts.