Yes, unfortunately, Hange met their end in the manga. It was a poignant moment for fans. The circumstances leading to their death were quite intense and had a significant impact on the story.
Survival and sacrifice are themes that can be found as well. In the world of Attack on Titan, survival is not guaranteed. Fanfictions may depict situations where Moblit has to sacrifice himself to save Hange or vice versa. This adds a layer of drama and emotion to their relationship. It shows the depth of their bond, that they would be willing to give up their lives for each other in the face of the Titans.
Well, a very common theme is friendship evolving into something more. In 'levi x hange fanfic', their initial friendship as part of a group gradually turns into a deeper emotional connection. Another frequent theme is the idea of facing challenges together. They are both in a tough world, and fanfics show them relying on each other to overcome difficulties. And there's also the theme of mutual respect. They respect each other's skills and abilities, and this is often highlighted and developed further in these fanfics.