Cant install Audacity program on my chromebook

I type the following command into the terminal

sfffdfddf@penguin:~$ sudo apt-get install audacity

Then it starts to download, when finished it says

Fetched 47.2 MB in 35s (1,357 kB/s)
E: Failed to fetch https://deb.debian.org/debian/pool/m....0-1_amd64.deb 404 Not Found [IP: 199.232.54.132 443]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

Then I tried the above advice but was told

sfffdfddf@penguin:~$ fix-missing
-bash: fix-missing: command not found
sfffdfddf@penguin:~$ --fix-missing
-bash: --fix-missing: command not found
sfffdfddf@penguin:~$ --fix-missing?
-bash: --fix-missing?: command not found
sfffdfddf@penguin:~$
sfffdfddf@penguin:~$ run apt-get update
-bash: run: command not found
sfffdfddf@penguin:~$

It has ran on this machine before but I had to remove linux and reinstall it as there was a problem