I can't install anything as I forgot my Administrator password

Is this what you did: Change or reset the password of a macOS user account - Apple Support? Please provide clearer and more detailed information. Please read Writing an effective Apple Support Communities question. We are here to help. We are all users. We are not mind-readers nor clairvoyants. We only know what you write down and tell us. Be specific and thorough. Include your hardware information and installed version of macOS. Try to write clearly. Think about what you want to say before you write it down, then re-read it to see if it makes sense.

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https://support.apple.com/en-us/HT202860