I have set the whole website to English. But the weird thing is the order and detail button inside log in via Shop in Chinese. Seems like no way to change it. I have tried to set default language to English.
Thanks for the help!
Your store’s default language will not always control the Shop or Shop Pay account interface. I would first test this in a private browser window with English as the only preferred browser language, and temporarily set the device or Shop app language to English as well.
If the buttons are still Chinese, take a screenshot and note whether it happens only when logged in. That points to Shop/Shop Pay localization rather than the theme language, so Shopify Support would need to correct it on their side.