Currently when restoring a translation on mobile, the active editor is set to the initial sentence (section title), even if users have translated already a lot of content of the section. This requires the user to scroll down to find the point to continue the translaiton.

This ticket proposes to set the active sentence to the expected one to be translated next. Keeping in mind that users have the option to skip sentences, the proposed approach is the following:
Set as active the sentence that goes after the last sentence with a translaiton. That is if sentences 1,2,5 have a translaiton, the active sentence will be 6.

In the case the last translation is the very last sentence of the contents, that will be the active one (there is no sentence after to select, and trying may result in Javascript Console to complain)