Yes it's great

Qui apprend une nouvelle langue acquiert une nouvelle âme seems to be one accepted translation into French. And sorry again for getting the wrong end of the stick.....

Almost. The word 'who' doesn't work as the subject. Here are some suggestions: "He who learns another language, acquires another soul" This sounds elegant, but is a little old-fashioned and rather sexist/male-orientated. Other possibilities are: 'Anyone who learns another language, acquires another soul" "A person who learns another language, acquires another soul" "Whoever learns another language, acquires another soul"