Searching about a book where they live on pyramids in space

Question

Basic premise is, that a lot of species live in pyramids in space that have been built by an unknown race. They travel with a rail system. The main protagonist is then "tasked" with repairing the pyramids. (at this point I am not sure anymore if they were pyramids)

Edit: The pyramids are in space rather huge, but only a small percentage is livable as the rest is locked of. The main character is a female police officer on this space station. At one point she gets stuck in an elevator and brought to one of the locked floors. There she meets one of the people repairing the pyramids. He was dying and she got the quest/job/responsibility to repair the building. She can travel through the whole pyramid through a door in her room.

The tram system was basically baskets travelling on a track. That was slow. The real was was to travel in the track.

An unknown alien race was trying to destroy the buildings and she starts defending it.

It turns out the cook of her favorite restaurant was one of the builders.

At this point this is all I know.

Answer 1

So I found the book, it is called Die Relikte der Erbauer.

In einer fernen Zukunft hat sich die Menschheit mit acht anderen Spezies zum Jamana-Völkerbund zusammengeschlossen. Der Frieden in der Galaxis erscheint gesichert. Gemeinsam erforscht man den Weltraum. Dazu nutzt man auch die Hinterlassenschaften der geheimnisvollen Spezies der Erbauer, eines Alienvolks, das vor beinahe zweihunderttausend Jahren spurlos verschwand und seine gewaltigen Apparaturen in den Tiefen des Alls zurückließ. Tia Orvat ist Mitarbeiterin im Sicherheitsdienst auf einer der wiederbesiedelten Raumstationen der Erbauer im letzten Winkel des vom Jamana-Bund erforschten Raumes. Als auf der Station ein Archäologieprofessor, der über die Kultur der Erbauer forschte, ermordet wird und kurz darauf die Leiche eines Außerirdischen einer unbekannten Spezies gefunden wird, wird Tia unfreiwillig in Geheimnisse hineingezogen, die weit in die Vergangenheit zurückreichen und den Frieden in der Galaxis ins Wanken bringen könnten.

Google translation:

In the distant future, humanity has joined forces with eight other species to form the Jamana League of Nations. Peace in the galaxy seems assured. Together, you explore space. It also makes use of the legacy of the mysterious species of builders, an alien people that disappeared without a trace almost two hundred thousand years ago and left its huge equipment in the depths of space. Tia Orvat is a security officer on one of the resettled builders' space stations in the last corner of the Jamana Confederation space. When an archeology professor researching the culture of the builders is murdered at the station, and shortly thereafter the body of an alien of an unknown species is found, Tia is involuntarily drawn into secrets that go far back into the past and bring peace into the galaxy Could bring faltering.

It's a German book, probably the main reason not a lot of people knew about it!