Why does my brew installation not work?

I installed brew before, but it does not work now. When I run brew, it gives me the error -bash: brew: command not found So I tried to reinstall using the code ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install) " But it gives me another one : > It appears Homebrew is already installed. If your intent is to reinstall you > should do the following before running this installer again: > rm -rf /usr/local/Cellar /usr/local/.git && brew cleanup If I use the command rm -rf /usr/local/Cellar /usr/local/.git && brew cleanup, it gives back the first error : -bash: brew: command not found What should I do now?