You need your email address and the password you set for ResearchGate. If you could write this request but did not log in "by hand", this means that your password is stored in your Internet browser and you are automatically logged in. For security reasons, there is no way to look up your password in your ResearchGate seetings (https://www.researchgate.net/settings/account), but you see at least which email address is used. You have to look up your password in your browser. Or see https://help.researchgate.net/hc/en-us/articles/14292811772689-Passwords how to set a new password.

Never give anyone access to any of your accounts. If your bank account is ever hacked in the future, the bank may not reimburse you and insurance could be cancelled if they find out other people know any of your passwords :)