Ionic 4 project Talkback reads text with english pronunciation instead of french pronunciation

We are working on an ionic 4 project. It should be accessible for blind and visually impaired people. When using Talkback in our app, talkback reads the text sometimes with English pronunciation and sometimes with french pronunciation.

For exemple, when i click on button :
Talkback says with english pronunciation : ‘Texte du button. Button.’
And after in french pronunciation : ‘Appuyer deux fois pour valider’. (touch two times to validate)

The device and talkback language is set to french.

Is there any possibility to change the language in talkback for all entries ?