A. If you're having trouble accessing your account, first ensure that you're using the correct username and password. If you've forgotten your password, use the 'Forgot Password' link on the login page to reset it. Follow the instructions sent to your registered email to create a new password. If you can't access your email, try the recovery options provided by Steam, such as answering security questions or using your phone number if it's linked to your account.
B. If you suspect your account has been compromised, immediately go to the Steam support page and follow the steps to recover your account. This may involve verifying your identity through email or phone verification.