Strange problem with popup "login" and "Register"

I'm a french Guy. I work for a french customer. I have a strange problem with the two popups "login" and "Register". i would like to have the two popups (login and Register) only in french language. Currently, inside the same popup, I have some texts in French language and some texts in English language. I do not understand.
Please, can you explain me how to fix this problem ?
Thanks in advance.

Did you translated template language file to french language ?

No because I have some texts in french and some texts in english ; so, I didn't search to do a translation.
Please, can explain me how to do this translation ?
Thanks.

Template language file is en-GB.tpl_hewahoo.ini in language directory.

Great. Thanks a lot.