why do you want to run multiple commands at the same time? If you can answer this, you may find a better way to do this.

yeah, I am just lazy and don’t want to sudo nano braveinstall.sh && chmod 700 braveinstall.sh

In your case, you can replace all the commands with sudo apt install firefox.

I hate the CEO of Mozilla, I hate them for running Firefox to the ground and they are politically active, so I don’t want to support them anyway. I don’t like to know the politics of tampons, ice creams & browsers, they should have kept their mouths shut.