Hello! Welcome to the Forum! 
Excited to hear that you are interested in translating!
We don’t want to instruct people to translate specific pieces so it depends on what you are interested in. Though I do recommend something thats easier to digest than whycardano.
For example, there are a few ‘summary’ style posts here in the Forum that help people get familiar with the project. I have done one on Incentives: Summary: PoS Delegation & Incentives (Lars Brunjes) or there’s another done by a community member on the beloved whiteboard video: Summary: Overview with Charles Hoskinson
But its completely up to what you feel comfortable doing!
Let me know if there are other questions!