Firstly - you are making your apostrophes the wrong way round :) they should go like this: eg it's, we're, Sam's coat. 1) If it's cold at night, turn on an electric blanket and you you'll get warm very quickly! --> there is nothing wrong here. You could say " you will get warm very quickly if you turn on the electric blanket when it is cold at night." 2)If you don`t go back at time to dinner, it will cool down --> this doesn't sound right. I would say " You dinner will get cold, if you do not get back in time" 3)If she comes, we will hear this instant the doorbell. --> again this isn't right. I would say " we will hear the doorbell the instant she arrives"/ "as she arrives we will hear the doorbell" 4) If this blouse matches the skirt, i'll buy it --> this is fine :) OR this blouse closes to the colour the skirt, i`ll buy it? --> this doesn't really make sense... "I will buy the blouse which is closest in colour to the skirt" I would actually say " I will buy the blouse which matches the skirt's colour the best"/ The blouse which matches the skirt's colour the best is the one I will buy" ( just an extra point blouse is a bit of an older word, it is still used, but not really by young people- we would just say the shirt, or the top)