Either form is acceptable.
If you mean "It is possible that you will be able to attend," use Possibly, you may attend. The word possibly is not necessary: its doubtful meaning is included in the form "may attend." Therefore, we make it absolute, separated from the grammar of the sentence by the comma.
"On a train" is correct grammar.
The grammar is correct as it is.
Grammar.
No. The correct grammar is; "Yes, I have a girlfriend."
Both "are" requested to attend the meeting.
If you mean "It is possible that you will be able to attend," use Possibly, you may attend. The word possibly is not necessary: its doubtful meaning is included in the form "may attend." Therefore, we make it absolute, separated from the grammar of the sentence by the comma.
No, "will be had" is not a correct grammar. The correct grammar would be "will have."
Both would be correct grammar, but "at your school" would probably be more suitable.
All is well
No, it is correct grammar, not a correct grammar.
The correct grammar is: "Are those correct?"
"On a train" is correct grammar.
It certainly can be correct. As with all grammar it depends on how it is used
no_____If the sentence is You do do that (meaning You are in the habit of doing that) the grammar is perfectly correct and the sentence 'does have correct grammar'.
No, the correct grammar would be: "July has just started."
This will be an exciting month is correct grammar.