Here is the solution to what I asked:  
To redirect to the right part of the website, in plugin User group named joomla under `OnUserLogin` event method add the following Code:

    $app = JFactory::getApplication();
    $app->setUserState('users.login.form.return', $options['return']);

I myself did not reach this answer, I learnt from Sergey Onichshenkov
Everything is working fine now.

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###Update:

Also to complete the answer , in case of joomla update, the code shall be gone, in order to get rid of copy and paste the code again, you may develop a custom plugin under the group User and design it as what is told in the initial answer.