Override translation

Hello,

Thank you for this great plugin !

I’d like to override a translation but I tried several methods and wasn’t able to do it. I tried to add bbp-private-groups-fr_FR.mo and bbp-private-groups-fr_FR.po files in :
/wp-content/languages/plugins/
/wp-content/languages/bbp-private-groups/
/wp-content/my-theme/languages/
/wp-content/my-theme/lang/
/wp-content/lang/plugins/
/wp-content/lang/bbp-private-groups/
without success.

What would you recommend ?

Thanks a lot for your help,

Regards,

David