Can you still open the game? Then do everything from there: Account → Change e-mail (if you still have the old one) or Account → Change e-mail → I no longer have access to the old e-mail. This page is only for when you cannot sign in from any device.
Enter your nickname, the e-mail you created the account with and the new e-mail. If nickname and old e-mail match an account, a confirmation link valid for 24 hours reaches the new e-mail; one tap moves the account to the new address, then you sign in from the game (Account → Sign in → 6-digit code). The old mailbox still gets a notice with a link to undo within 72 hours. For safety the answer below is always the same: if nothing arrives, the details do not match (check the spam folder and the capital letters in the nickname).
No old e-mail left and you don’t remember the nickname? Write to [email protected]: we verify your identity and send you a link code.