Trouble With Updating Linux, Accessing Software Center, ETC.

BipolarPotato

Alright, so I'm having a bit of difficulties with updating my linux and accessing many of my programs. For example; When I try and access the Ubuntu Software Center, it begins to load before closing all together. I tried updating my system but I only got an error message:

Reading package lists... Error!
W: There is no public key available for the following key IDs:
1397BC53640DB551
W: There is no public key available for the following key IDs:
1397BC53640DB551
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/repo.steampowered.com_steam_dists_precise_steam_i18n_Translation-en
E: The package lists or status file could not be parsed or opened.

Due to this, I haven't been able to update any of my software nor have I been able to use or install new software.

Please help!