First off, thanks so much for putting together the English-Russian course. I love how it makes me thoroughly practice all the cases and aspects of all the words. I love Lingvist compared to other language learning apps because it is straightforward, has a pretty interface, and provides good background information about each word.
The one request that I would make is that there would be some indication whether a sentence was seeking the informal vs formal You pronouns. Similarly, some indication if a sentence was seeking the "go by foot" vs "go by transport" verbs of motion. These changes may minimize frustration.
Thanks for creating such a great learning experience!