translation exercises are very useful.
because when you translate a sentence you translate not only words, you use also grammar, syntax knowledge. and teachers use it because they see what they should work with their students on, if the students understood the material.
according to my experience i started writing long emails when i got internet connection at home, 1st i wrote email in russian, then translated into english in writeen, then typed it. the more u do it the more useful it is. so in about two months i stared forming english sentences without writing in russian, i started thinking in english. what is very important.
hope it was useful for you
all the best