the bc at first was in english , afrter switching to fr it shows a mixt beween fr and eng and even after switching the language to french or english B.C keep using a mix between the two of them causing confusion and problems for our clients , and i don't know how to fix it
From the likes of your screenshot, the CRONUS installed is a UK version, typically not equipped with French translations.
You might want to switch to 'another' French, given the fact that multipe 'French'-variants exist.
If that does not work out... you will have to proceed as stated in the answer below: install the language (and please be cautious in selecting the 'right version of French' for you)