No. Us is the objective case, not the nominative case (we).
It should be:
We teens need more sleep. Or:
We, as teens, need more sleep than others.
I am, you are, he/she/it is, we are, they are.
The phrase "how don't I" is not grammatically correct. A more correct way to phrase it would be "why don't I."
No, "most friendly" is not grammatically correct. The correct form would be "friendliest" when comparing three or more things.
Yes, "is much more easily" is grammatically correct because it follows the correct order of adverbs (much, more, easily) when comparing multiple items or degrees in a sentence.
Yes, the phrase 'what they're doing' is grammatically correct. For example: What they're doing is wrong.
I am, you are, he/she/it is, we are, they are.
The phrase "how don't I" is not grammatically correct. A more correct way to phrase it would be "why don't I."
No.
No, "most friendly" is not grammatically correct. The correct form would be "friendliest" when comparing three or more things.
Yes
The second one is more correct.
Yes, "is much more easily" is grammatically correct because it follows the correct order of adverbs (much, more, easily) when comparing multiple items or degrees in a sentence.
Yes, the phrase 'what they're doing' is grammatically correct. For example: What they're doing is wrong.
No, it is not. The "question word," why, should be at the beginning of the sentence. Why was she promoted?
Both "you and he" and "he and you" are grammatically correct, but "you and he" is more commonly used in English.
Both are grammatically correct, but "do not feel" is better usage than "are not feeling."
The sentence "Thanks to rain and its cold at once, it's going to be a good sleep for me this evening" is grammatically correct. However, it may sound more natural if you say "Thanks to the rain and the cold weather, I should sleep well this evening."