and Arabs are especially good in trade. or good at trade?
Both are okay. "at" might be a little better.
The correct word is expertise. (no need for "s")
Stimulating can mean interesting.
It is not uncommon for a country to develop
missed mixed nationalities and cultures in recent years.
(Practice typing the sentence above a few times to gain a useful grammar-habit.) :-)
People from different countries have their own values. Accordingly, they may not understand others' behaviour, which...
... could be regard as a barrier for communication among various cultures.
If not dealt with appropriately, it may cause ethnic conflicts.
Keep practicing! You have mistakes, but the meaning is very clear!