When sending approvals, Power Automate uses the following hierarchy to make a decision about which language to send the approval in:
The recipient's language as configured in the Power Automate portal.
The recipient's language as configured in the Office portal.
In the case of manual triggers like "For a Selected Item" in Sharepoint, the caller (e.g. Sharepoint) will pass the user who invoked the flow's language in the request, which Power Automate will honor.
Finally, for automated flows, Power Automate will default to the creator of the approval's language as determined by steps 1 and 2 above.
Changing Your Approval Language
If you are receiving approvals in an unexpected language, the recipient should modify their language in the Power Automate portal.
To achieve this, click the gear icon in the top right of the Power Automate portal, click "View all Power Automate settings", and select your preferred language. These values are cached, so it may take as long as 24 hours for the new settings to be reflected, though it should generally be much quicker than this.