Can only the people of their own guild trade in the trading post?
Or people from other guilds, can't find anything?

Anyone can trade at the trading post. But only the guild members of the owning guild can manage the offers and Access the storage room to take receive sold items.

Ah, I wanted to use the trading post so that the different guilds/users could trade, but that's not possible because the building would stand on neutral ground. Thanks for the info!

Yes, on neutral territory, only the server market can be used.

okay I have the trading post now but on the server I had overlooked that there is also a server trade, that helps us already immensely. I have now created a central trading post on the map where everyone has to go if they want something, movement is healthy.
The whole great work, finally the trading post has a sense. Thumbs up!
Sorry for the bad english but I last had it 1970-75 in school so deepl.com translated the whole thing.