I have a question and please, I want towould like some help me.

I have a big problemdifficulty with tenses.

Yesterday, my friend send t this message.

"I have been busy here at the office !!!

More natural to say: "It's been busy here at the office!"

He and I wWe don't live in the same counrtry, so we have a big differente with hourthere's a large time difference.

I hope everyone understands me.

"I have been busy here at the office !!!

"It's been busy here at the office!"

I have a question and please, I wantwould like someone to help me.

I'm assuming you want other people to help you with your question rather than you trying to solve it by yourself, since you're asking it here.

Yesterday, my friend send hist me a message.

".

Spacing issue. Put the closing quotation marks after the exclamation marks in the message.

He and I we don't live in the same counrtry, so we have a big differente with hourtime zone difference.

I hope everyone understands me.

I canwould say: I am working.

OrI could also say I am busy now.

"Or" is fine when in conversation but not in written English.

wWhy did he put in the present perfect?

I want you to explain this to me in very simple please.terms.

https://www.woodwardenglish.com/lesson/when-to-use-present-perfect-tense/
This grammar link about why people use present perfect might help you. I think present perfect emphasizes that you were doing something in the past but it's important to the present- like a past action that you just completed. For example, "I have been studying" would imply that I was studying recently.