When in Rome, do as the Romans do
means that when you are visiting a new place, you should try to do as the people do who are from the place
Example: "I can't eat that." Reply: "Oh, give it a try. When in Rome, do as the Romans do
(عندما تكون في روما إعمل كما يعمل الرومان)
يقابلها بالعربي
(يا غريب كن أديب)