I found the fix for this... at least for the App Store. I guess it should work for iCloud too!
1. Go to https://appleid.apple.com, then log on, then go in the language settings and check if it says "French". If so, set it to English, and save your change.
2. Then on your iPhone, go to Settings->Store->click on your Apple id->Select "Sign Out"
3. Then I rebooted my iPhone ...it changed the Apps in the App Store to their English version but the options bar was still in French... that was encouraging...
4. ...so I decided to reset my iPhone and restore from the previous backup. I did the reset not through iTunes (just in case) but directly on the iPhone through Settings->General->Reset->Erase All Content and Settings. It took a few seconds, boot back by itself (and after a few setup questions) asked me to plug into my PC and restore through a backup I had in iTunes.
...After step 4, the options bar of my iPhone App Store was also in English... Hurray !!! 🙂😁😉