According to formal grammar, who is used in the subject position, while whom is used in the object position. In modern English there are many speakers who rarely use whom at all, using who in all contexts; today this use is broadly accepted in standard English.
I think - Please take care of whoever is waiting - is better.
This sentence is grammatically correct.
Yes, it is.
You had not taken that into account. Would be the grammatically correct version of that sentence.
Der Junge ist rothaarig is grammatically correct.
"That was wrong" is a grammatically correct sentence.
This sentence is not grammatically correct. For the sentence to be grammatically correct, the space between "in" and "to" would have to be removed. Therefore the sentence should read "They are into skating."
The correct grammar for the sentence is: "Please note that this letter is merely an inquiry regarding your interest and availability."
The sentence is grammatically correct.
yes
The sentence (not sentance) is grammatically correct
No, "firsts" is not grammatically correct. It should be "first."
Yes. "I do not like people" is complete and correct, albeit anti-social.