No. The correct grammar is; "Yes, I have a girlfriend."
Yes, grammar is the correct spelling.
yes
Yes, "best possible" is correct grammar, as in this sentence: This is the best possible outcome considering the circumstances.
Yes, it is correct grammar to say "Would you be so kind as to [do something]?" It is considered somewhat formal.
yes, "you discribed to my mother and me" is correct grammar, however the form of the question could be made more clear.
Yes, that sentence is correct grammar.
Yes, that is correct grammar.
Yes, that sentence is correct grammar.
No, the correct grammar would be "I hate you the way you hate me."
Yes, 'you were correct' is perfect grammar. An example sentence: You were correct when you said that a tomato is a fruit.
yes that is the correct grammer im pretty sure
Yes. What is not correct is your putting the article "a" before grammar.
Yes, grammar is the correct spelling.
yes. After with regards you would put your name.
Yes.
Yes.
Yes, "he butts in" is correct grammar, although it is somewhat informal language.