When typing in English, once you type a word, you can go onto the next unless if you made a typo. In Japanese, you have to convert the word into kanji before you can go onto the next. Doing that takes up precious seconds and the seconds add up to minutes and the minutes add up to hours.
I'm not all that familiar with Japanese grammar, either. I'm glad I'm not translating something that needs proper grammar. *whew!*
Anyhoo, it's taking me forever to finish an English to Japanese assignment and it can get to be irritating because of the slow progress. I hope they give me more Japanese to English assignments than vice versa. I'm missing the times I was just twiddling my thumbs with nothing to do. LOL