Computer-janitor not working

go to filesystem then /usr/share/computerjanitor and look for a file named computer-jantor-gtk. run it and you will get a GUI to clean the system.

In share, I have 'computerjanitor' (not computer-jantor-gtk) and in it there are 6 files ( ~egg-info, ~app, ~ord, plugins, computer-janitor, janitord ). Which one should I open?

I suggest you install bleachbit, I find it does a better job but watch the settings you use or it can remove settings you want and avoid options which say they will take a long time

Installed BleachBit. A good one indeed. But APT/autoclean & autoremove couldn't clean completely. BleachBit's Output is:

E: Could not open lock file /var/cache/apt/archives/lock - open (13: Permission denied)
E: Could not open lock file /var/lib/dpkg/lock - open (13: Permission denied)
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>Run the app as root and your user and have as many apps CLOSED as you can.

   Would you please make it clear?

the bleach bit requires to be run as root to work efficiently.
 you can find 2 options in installed programs for bleach bit. 1. bleach bit
and 2. as root(bleach bit).
run it as root and see the magic.

alternatively launch bleachbit from terminal a

sudo bleachbit

and enter the admin password.

Also make sure you don't have software centre open and that no updates are running

Thanks actionparsnip, that solved my question.

Thanks Actionparsnip. Your suggestion solved the problem. I saw BleachBit(as root) just after I sent my last message.
Murali Krishna, you are right. BleachBit is a good one indeed. Thanks.