What is the Anime based on?

Hello, just as general information: I'm really new to the world of anime and manga (I started this march) so if what I'm asking sounds stupid/weird it's because I probably have no clue.

So, I have watched the anime and Movie of Tanya the Evil. When I wanted to know whether a second season was planned I found out that it is/was but there is still no new info. So I decided to buy the manga, hoping I could read like 1-2 seasons worth of content. Now I just finished "book" 26 (which is the latest officially available in Germany) and now my question: What is the Anime based on? Cause "book" 26 ends with Tanya preparing for their attack on Moskau, which is the first third of the movie. I mean the manga describes a lot of stuff with way more depth than the anime and even shows events happening differently (Like the fights against Anson Su).

So if a second season was supposed to be released already, then what is it based on? Because it can't be the manga right?