Reference: Sharh ‘Umdatil-Fiqh – Tape No.4, Question No.43
Question: What is the ruling regarding learning foreign languages for the sake of da’wah?
Response: If it is for a [genuine] need, then there is no harm; there is no harm in learning them for a genuine need. As for learning them [simply] because you like them, then that is not permissible.