correct sentences

You can send me an offline message if I am not online.

or

Send me an offline message if I am not online.

but not 'you send me'.

Thank you friend.

Tomorrow I may be busy. So I may be offline all day. You send me offline messages if I am not online.

Do you mean the violet coloured parts are unwanted in this context?

Also, why "you send me" is incorrect which sounds correct.

No, the violet parts are fine.

'you send me' is too much of an order or, actually, it sounds like a comment on what the person already does. You give me presents on my birthday. You send me offline messages. It doesn't sound at all natural as a request.

Again, thank you friend.

If you say "Send me an offline message", I will still understand it as "You send me an offline message". I will consider as the subject "you" has been omitted. So can I use "please send me......" to be more polite; or to be seen like a request.

It will be very much better [indeed, politer] to say "Please send me ..."

We have 8 notebook left in our stock.

We have 8 notebooks left in our stock.

have myself a cup of fresh brew coffee and a bagel for breakfast

Hi,

have myself a cup of fresh brew coffee and a bagel for breakfast

eg Every morning, I have myself a cup of fresh-brewed coffee and a bagel for breakfast.



To me, this is a casual, folksy kind of speech.



Clive

I feel that it is better if you change that like this "I will be busy tommorrow."just for your reference.