Here is a step-by-step explanation of the corrections and adjective comparisons:
Correct the Mistakes in Sentences:
My father doesn't like coffee. He never drinks it.
This sentence is correct as it stands.
Ba gets up at 6 o'clock and gets dressed.
This sentence is correct as it stands.
Would you like some noodles? - Yes, I wouldn't. I'm not hungry but I'm thirsty. I'd like a cold drink.
Correction: "Yes, I wouldn't" should be changed to "No, I wouldn't," because if you're not hungry, you wouldn't want to accept noodles.
What do you do when it's cold?
This sentence is correct as it stands.
Where is your classroom? - It's on the ninth floor.
This sentence is correct as it stands.
How do you say the word 'yard'? - Y-A-R-D.
This sentence is correct as it stands.
After getting up in the morning, Hoa washes her face, brushes her teeth, and then has breakfast.
This sentence is correct as it stands.
How much homework does Ba have every day? - He has a lot of homework.
This sentence is correct as it stands.
How often does Mr. Ba go to Ha Noi? - Seldom, once a year.
This sentence is better worded as "Rarely," as "seldom" is less commonly used in modern English.
Are you and Hoa in grade 6? - Yes. We are in class 6A.
* This sentence is correct as it stands.
Write the Correct Form of the Adjectives in Brackets to Make Comparisons:
I think she is still ill. She looks even worse than last week.
(Correct use of the comparative form "worse.")
His results are not as good as his colleague's.
(Correct comparison using "not as good as.")
Which of the three supermarkets do you think has the widest range of products?
(Correct use of superlative form "widest.")
He has bigger potential than anyone thought.
(Correct comparative form "bigger.")
It's becoming harder to attract new customers. What we need is a new strategy.
(Correct comparative form "harder.")
In the last few months, competition has become tougher.
(Correct comparative form "tougher.")
Things are better organized now - we have fewer problems than before.
(Correct comparative form "better" and "fewer.")
There are more accidents on this road because it's narrower than the others.
(Correct comparative form "narrower.")
I chose this car as my favorite because it's faster than all the other ones I have driven.
(Correct comparative form "faster.")
She's a lot happier in her new job than she was in the previous one.
* (Correct comparative form "happier.")
In summary, the sentences provided were mostly correct or required small adjustments for clearer communication. When comparing adjectives, using the appropriate comparative or superlative form is key: "-er" for comparative and "-est" for superlative, or "more" and "most" where applicable.