gui design – Decrease the font size or break to a new line for multi-languages?

I would like to know what is the better way to deal with the following issue:

a website support multi-languages, some of them fit in one line of a container but others are not.

Is it better to reduce the font size on those which aren’t fit? (which I believe may ruin the user experience) or keep the size but break it to a new line?