Foreign language in WhatsApp

Hi. I have followed the standard via Setting on the iPhone to get a foreign language. Whilst the different language goes throughout the phone, it does not appear on the WhatsApp base messages. For instance, if I would like to message a French person, the French appears on each app however the language does not exist on WhatsApp messages. So I cannot get a word with accents. Only English is at the WhatsApp base. What is the suggestion for this issue?