There is currently no method of changing your language within the Adopt Me experience itself. You can however adjust your Roblox settings to match your language, and this will automatically update the game to be suited to your language.
To do this, you can head to your Roblox settings where you'll land on the Account Info tab. Scroll down until you reach the "Language" section, and choose your language on the drop-down menu. Roblox offers a detailed guide here.
Please know that translations for many languages are done through Roblox's automated system, so there may be errors at hand. There are some languages translated by ourselves, and you can find the languages we support here.