I don't get how you use this immersion option.
I am learning French.
Look for blue lines, those are the ones not yet translated. The grey/black lines will already have been translated by others, but you can still edit them -if- there are mistakes in them, or just click 'Looks good' if they look right to you.
If you go to the Immersion page and set the 'All documents' tab to sort by newest first (I don't remember if this is the default), then the top articles should be freshly uploaded and have a lot of blue sentences for you to start translating.