1) I am not sure about the answer to that question.
2) I do not understand what you are asking me.
3) Have not seen my friend in a long time.
4) Can not believe how fast time is flying by.
5) I am not a fan of spicy food.
6) I do not have enough money to go on vacation this year.
7) Have not finished reading the book yet.
8) Can not imagine living without my phone.
9) I am not interested in joining the club.
10) I do not have any plans for the weekend.