The Home App automatically adopts the language set on the mobile device. You can make this change under "Settings" on your mobile device.

With iOS you can change the language as follows:

Tap on "Settings" > "General" > "Language & Region" > " [Device] Language".
Set the desired language and tap Done.

With Android, you can change the language as follows:

Tap on "Settings" > "General Administration" > "Language and Input" > "Language" > "Add Language".

Add the desired language and set as default.