Grammar is tricky. If you did not learn it as a child, the best way to learn it (and know whether your grammar is correct) is to find someone who speaks correct grammar and listen to them, a lot.
NPR is a good place to listen to people who have good grammar.
The sentence "I arrived exactly at their cut off time" is not correct grammar because of the wrong diction used.
There are essentially two approaches that are available to you, for the purposes of writing letters with good grammar. You can learn grammar, or you can write a letter to the best of your ability, and then get someone else, who does know grammar, to edit it.
"The couple don't know" is correct.
"G-R-A-M-M-A-R" (You should know, since you spelled it out in your question.)
Kindly let me know further update
Yes, it is grammar, but your spelling is wrong; it's spelt grammar.
Wrong grammar!
Wrong Grammar
nothing ! because your wrong grammar !
You were - This is correct. You were the best in the team.
yes
No, because your grammar is wrong. DID+QUALIFIED=IDIOTIC GRAMMAR
The word his can only be maid a grammar mistake if spelled wrong or capitalized
There is nothing wrong with "when will you come?"
Wrong spelling is the incorrect spelling of a word. Wrong grammar has a much broader meaning and can include using a word in the incorrect tense or sense, or inserting or omitting punctuation.
Do you know what correct grammar is? Do you know what correct grammar is?
Don't know but I suggest you use proper English and spelling of words. The question is "...many more years YOU'RE going to live". Much and your are just plain wrong grammar and spelling. The wrong word spelled right is still the wrong word.