When you go to foreign country and was asked by someone 'what brought you here?',
Is there any other form of answer which has same meaning with 'I’m here on business'?
When you go to a foreign country and are asked the question, one of the most broadly used replies is
I am on a business trip.
A business trip is the opposite of a vacation or personal trip for which you have to spend your own money while a business trip is paid for by your company.
There could be more expressions depending on purposes of your business trip, but you don't need to specify your purpose unless it is specifically asked by another party.
We can alternatively say things like:
I'm here for work.
My company sent me.
My boss sent me.
If you want to show extra friendliness or encourage further conversation with someone, you might say things like:
I'm here for work this time, but I would like to come back someday for a vacation and get to know some of the friendly people here.
I'm here to work, but I will have some free time this weekend. Do you have any suggestions for places I should visit?