Summarize this article in one sentence.
The only way to change the language of the Google app on iPhone, iPad, or iPod touch is to change the language for the entire device. For a workaround to keep your system language intact, see the last step of this section.  This will display a list of available languages. This will change the language for every app on your device, and is the only way to change the language of your Google app. See the next step for a workaround if you want to search in another language. If you want to be able to search Google using a specific language, but want to keep your device's language set as it is, you can create a shortcut on your iOS device's Home screen that will take you to the Google search page in the language of your choosing:  Open Safari and visit the Google site in the language you want to use. Google is available in many different countries, and uses the domain assigned to that country. For example, the German Google site is Google.de, the Japanese Google site is Google.co.jp, and the French Google site is Google.fr. Tap the Share button. This looks like a box with an arrow coming out of it. You'll find this at the bottom of the screen on iPhone and iPod, or at the top of the screen on iPad. Tap "Add to Home Screen". You'll be given the option to change the title. Add the language to the title so that you can quickly see what version of Google you will be opening with the shortcut. Tap "Add" after you have made the changes. Use the new shortcut whenever you want to search in another language. Tap the new shortcut on your Home screen to instantly open the Google site in that language. All of your search results made from that bookmark will be in the language you chose.

Summary:
Open your iOS device's Settings app. Select "General" and then "Language & Region". Tap "iPhone/iPad/iPod Language". Select the language that you want to use. Create a shortcut to the Google site you want to search on.