This is the text with the mistakes highlighted :
Nelli (Необучаемый взрослый ученик. Что делать?)
Since no real explanations or corrections were provided I had to make some guessing work on my own. So I've guessed that "I've notice" should be "I've noticed", "the author use" -> "the author uses" (which are typos but as I said - who cares?), and "trouble to fit"/"trouble to match" -> "trouble fitting"/"trouble matching". But. Could someone explain to me what's wrong with "the tenses would be"?"... I've notice that usually when I'm reading a text written by a non-native speaker (with good command of English) I can understand, or easily guess, why for example the author use that or this tense, and all the tenses would be neatly put according the "textbook" rules. But it isn't the same with the texts written by native speakers, including professional writers. Often their choice of tenses, articles, etc. might come as a surprise and seems to go against the rules. Or maybe I just don't understand the rules :) . Either way, while I have some trouble to fit such a sentence into the consciously learned rules I usually have little trouble to match it to my inner "grammar rules" - the rules I had built/figured out during the first 4 years (almost 4 and a half actually) when I just read books and watched tv shows."