problem after apt-get update command

Recently , i tried to install google earth from Ubuntu tweak . the programme asked me to add the repository of google earth . well,after i do the command i found that an error message that told me that i couldn't add the source and the system can't build packages tree.i run in terminal sudo apt-get update and i found following Errors:

Fetched 143 kB in 3min 43s (637 B/s)                                           
Reading package lists... Error!
W: GPG error: http://ppa.launchpad.net trusty Release: The following signatures were invalid: BADSIG 6AF0E1940624A220 Launchpad PPA for TualatriX
W: GPG error: http://eg.archive.ubuntu.com trusty-backports Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <[email protected]>
E: Encountered a section with no Package: header
E: Problem with MergeList /var/lib/apt/lists/eg.archive.ubuntu.com_ubuntu_dists_trusty_multiverse_i18n_Translation-en%5fUS
E: The package lists or status file could not be parsed or opened.

I can't launch Ubuntu software center.and a minus mark appear in bar at the top of the screen . please tell me what should i do in steps please.i have Ubuntu 14.04 trusty tahr.

For the GPG errors, run sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 6AF0E1940624A220 40976EAF437D05B5 to import the keys.

For the MergeList problem, run sudo rm /var/lib/apt/lists/*.

Finally, run sudo apt-get update.

To summarise the instructions from saiarcot895 :

For an error like this

W: GPG error: http://archive.ubuntu.com trusty Release:
The following signatures were invalid: BADSIG [ some_number ] 
Ubuntu Archive Automatic Signing Key <[email protected]>

do this - preferably one instruction at a time -

apt-key adv --keyserver keyserver.ubuntu.com --recv-keys [ some_number ]
cd /var/lib/apt
ls -la
sudo mv lists lists_bak
sudo mkdir -p lists/partial
apt-get update

which is roughly

1. call gpg via apt-key via apt-get, to download a new key
2. go to where apt keeps its data
3. look at the data that apt has at the moment
4. rename the apt cache directory to both back it up and clear the cache
5. make a new apt cache directory
6. update the cache of packages that apt knows about