It's very important you copy these commands carefully, with the wrong folder paths you can do some harm to your system.
This will purge the old cache so to speak.
sudo rm /var/lib/apt/lists/* -vf
This will then update the caches again for the repos. Then procede to run updates as you normally would.
sudo apt-get update
I copied this from another post, what happens here is that the file might've gotten messed up while being downloaded. It's funky to say the least, but does happen on almost all debian/apt based distros.