Can you now open a web page and just copy and paste the lines from Braves website and use the terminal?
You can either use the script vasileios made here:
Or go directly from Braves website here:
Here are Braves steps which are exactly what vasileios included in the script:
sudo apt install apt-transport-https curl
sudo curl -fsSLo /usr/share/keyrings/brave-browser-archive-keyring.gpg https://brave-browser-apt-release.s3.brave.com/brave-browser-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/brave-browser-archive-keyring.gpg arch=amd64] https://brave-browser-apt-release.s3.brave.com/ stable main"|sudo tee /etc/apt/sources.list.d/brave-browser-release.list
sudo apt update
sudo apt install brave-browser