When you set language to English and back to home page without "?lang=en" it's being set automatically to my language again. This also happen if I set any other language e.g "?lang=ar" to Arabic.
What is happening is that https://xat.com/?lang=LANGUAGE_CODE is not storing the Cookie, so when you back to the home page it still showing on my language, not what I've set, this also mean that the chats will be shown in my language, not the language I've set.
I'm using Firefox 68,
Step 2: Back to https://xat.com