Translation:When I was not married yet, I ate at restaurants much more expensive than I do now.
"When I was not yet married. I ate at more expensive restaurants than I do now" uses the same words and is better English, but it was rejectrd. "much more expensive restaurants " is better than 'restaurants much more expensive' because the latter feels as if "that are" is missing from the sentence. Sadly, being a native speaker of any language is no guarantee of speaking it well or even correctly.-- notice the mistakes that many Czechs make in using their own language.
Last I heard, it was not possible to switch to keyboard input in the apps, but you can if you use Duo on a mobile (or desktop) browser. As VladaFu suggested, it could help to post your question in the general or troubleshooting forum. This is a technical issues, and the course team cannot help with it.