A: I am so tired. B: Why is that? (I don't think it is natural to use "that" in this situation. "So tired" is difficult to quantify.) The second question and answer pair is fine to me. I want to buy some snow boots in the/a sale. (or "a pair of snow boots"). The next sentence is fine grammatically. It is difficult to "cure" a pimple, however. Perhaps "I want the pimple on my face to clear up as soon as possible." "We can only update our notebook twice a day on italki." is my preference.

A: I'm so tired..... B: Are you that tired? A How did your presentation go? B: It went well. Thank you! I want to get a (pair of) snow boots on sale. I want to cure the pimple on my face as soon as possible. We only can update our notebook twice per day on italki.

Only the following two call for correction: -- I want to get snow boots on sale. -- I want to get rid of the pimple on my face as soon as possible.