In Terminal I follow this suggestion to recover files from a failed HDD with DDrescue.
When trying install Homebrew I am asked for a password. I don't know wath to do. I am a first user.
What to do to go forwards?
When you setup your Mac, you should have been asked to create a password for your account.
If you do not remember that password, then this is how you reset your password to a new value that hopefully, you do remember https://support.apple.com/en-us/HT202860
Also, when HomeBrew is asking for a password when you type the password, you will not see anything echoed back, but the Mac is seeing every key you type. After entering the password, press the Return key.