Since you are posting to the Garmin Connect Web, I assume you want to change the language of the website. In that case you can do it in the user profile: https://connect.garmin.com/modern/settings
If you want to change the language on your watch, like the original poster, please look it up in the user manual of your watch - the exact location may differ according to the model you use, but usually you can find it in System Settings.
