First in priority is correct. Priority is a much-misused word. It is something to have, or to be in, not something to be. Better speakers never say something is a priority, but rather that it has priority.
He agrees with you. Or he is in agreement with you.
"That was wrong" is a grammatically correct sentence.
Yes, Almighty God is grammatically correct.
Yes, it is grammatically correct.
This sentence is grammatically correct.
It can be, like in the following sentence. There were many firsts in this historic week.
No, I think the correct way is- Is this the first time you've seen it?
Yes, 'for free', is grammatically correct.
"Not like that" can be grammatically correct, depending on the context.
Yes! That is grammatically correct!
He agrees with you. Or he is in agreement with you.
Needs to be a grammatically correct question!
This is not grammatically correct. The correct form is 'you do not know', or the abbreviated 'you don't know'.
'What a drunkard you are' is a grammatically correct English sentence.
"That was wrong" is a grammatically correct sentence.
Yes, it is grammatically correct.
Yes, Almighty God is grammatically correct.