Hi Lilian,
I do not know in particular Dalberg Advisors cases examples but, generally speaking, 2h written cases are an extension of the typical case interviews, with the addition of 2 important skills to develope:
1. 80-20 prioritization: identify the most important data and topics to focus on during the resolution
2. final slides preparation: craft a mini deck of top down impactful pages to present at the end of the interview
here you can find some tips from Bain: https://www.bain.com/careers/interview-prep/written-interview/
Hope this helps
Antonello