Problem with words learned

Hello guys,

I started learning russian 50 days ago. I reached a point when my fresh account had 1600 words learned then it was russian 5 that there was part 16 that is missing one word and could not be completed that I press to learn it again in case the date gets wiped off but nothing worked. When I went back to my main profile the words went from 1600 to 1200 learned.

How is this possible? Can it be fixed? I am a premium user and I strictly use the website.
Also the application always showed that I know less words than the website.