are you using mnemonic? I used to use the mnemonic english -> russian keyboard but like 3 of the letters aren't even on the windows layout, so it's worth it to learn how to type in the traditional layout. You should look up russian typing lessons and just go with the normal rus layout
I use the Russian Mnemonic keyboard and it works fine for me. You just have to remember a few two-key sequences to get it right, like "sc" for щ, "jo" for ё, "ja" = я, and "ju" for ю. Also, "s + (space-bar)" = с, "c + (space-bar)" = ц and "j + (space-bar)" = й. The rest are single key-strokes.
The only time I've had problems is when I've switched back to English and then forgotten to switch back to Russian, so I've entered an English "e" for a Russian "e", and that's a misspelling under Duo.
I find the mnemonic more sensible for my beginning stages, because so many Russian letters are the same as or equivalent to English letters, it's easier to remember.
Надевай is the imperative form:
- Тим надевает свитер ‘Tim puts on (his) sweater’ is a fact,
- Тим, надевай свитер ‘Tim, put on (your) sweater [continuosly]’ is a command.
Note that надевай is imperfective so it would be used when you want Tim to put on his sweater all the time (so it sounds a bit strange unless you add some limitation, e.g. «надевай свитер зимой» ‘put on your sweater in winter’). If you want Tim to put on his sweater just one time, you‘d use a perfective verb:
- Тим, надень свитер ‘Tim, put on (your) sweater [one time]’