Your windows language is English but your native language is French and you wonder how can you change The Teamviewer language from english to French.
How to change language in the Team Viewer
1- Open Team viewer and Click Extras.
2- Then click the Options.
3- And click the Advanced.
4- Then click the Show advanced options.
5- Here you can select your Language using the dropdown list display language
6- Restart Teamviewer.