1. I called on one of my friends in Quebec. - This is fine. 2. What's the difference between yesterday, I ran across Dave in the city. yesterday, I ran into Dave in the city. - It would probably be more common to say 'I came across...' rather than 'I ran across...' but people would know what you mean. 3. If I put this poem into Japanese, I will be little strange. - "If I put this poem in Japanese, it would be a little strange" or probably more correctly - "If I translated this poem into Japanese, it would be a little strange" 4. There are some people who counter my opinion. - I think this is fine, though variations might be "There are some people who have a different opinion" or "There are some people who argue against my opinion". 5. There was a considerable rise of the birthrate in 1990. - "There was a considerable rise in the birthrate in 1990" 6. He always lags behind his work. - "He always lags behind in his work" or - "He always lags behind with his work" 7. the civil war in south Africa arose from the religion. - "the civil war in South Africa was caused by religion." 8. As my grandma has to take care of my grandpa all the time, he is a burden for her. - This is fine. "...he is a burden to her." is also ok. 9. If you just smile when you don't understand what others say, you imply you did understood everything. - "If you just smile when you don't understand what others say, you imply that you understood everything." 10. Teachers at school always impose their rules on pupils. - This is fine.