It sounds like your Odoo instance may still have French installed as an active language, which is why certain pages are switching over. A good first step would be to check Settings → Translations → Languages and see if French is enabled. If it is, you can either deactivate it or remove it entirely, and then make sure English (UK) is set as the default. Also, clearing your browser cache or restarting the server can sometimes fix lingering translation issues.

Have you noticed if the switch to French happens only on specific modules, or does it occur randomly across the system?

Hi,

    In your user profile change your language to english.

    Then disable the French language in your settings > Translations > Languages

Hope it helps.

Hi

try setting/ general Setting/manage your language.--> Disable French? 

Best 

Acus Conseil