Suppose your language name is "my_lang"
Copy application/language/english folder and paste & rename folder to "my_lang".
Then translate all files in that folder.
Translate coping plugins/grid/locale/english.js as plugins/grid/locale/my_lang.js
Translate coping plugins/grocery_crud/languages/english.php as plugins/grocery_crud/languages/my_lang.php
Then open application/controllers/home.php
and add an array index like:
"my_lang"=>"My Language" in _language_list() function

If you want to add languages in html replace the text with echo $this->lang->line("text");
If you want to add languages in php replace the text with $this->lang->line("text")
Then add that word to misc_lang,php or any other lanuage file like:
$lang['text'] = 'yourDesiredText';

Suppose you want to change the language in visitor analytics overview page. Suppose you want to replace the text "Day Wise New Visitor Report From" or "Total Unique Visitor"
Then open application/views/domain_visitor/visitor_analysis_details/overview.php and replace the texts with :
echo $this->lang->line("Day Wise New Visitor Report From");
echo $this->lang->line("Total Unique Visitor");
Then open application/language/turkish/misc_lang.php add the lines at bottom of page like::
$lang['Day Wise New Visitor Report From'] = 'yourDesiredtext1;
$lang['Total Unique Visitor'] = 'yourDesiredtext2;

Open application/config/my_config.php and you will find the variables.

To change the number of keyword just open the file application/views/admin/keyword/keyword_list.php
In this file in line number around 58 there is a condition if($number_of_keyword < 3) here you can set the number of keyword.
Then , open the file application/views/admin/keyword/keyword_tracking_settings.php
In this file in line number 85 there is a condition if($number_of_keyword < 3), here you can set the number of keyword.
That's all, but don't add too many keywords or google will block your IP while your cron job will run.

There are total three themes for front end ( one for landing page and for front pages like sign up) and back end.
Landing Page's Theme:
HTML/PHP: application/views/site/site_theme.php
CSS/JS: assets/site/
IMAGE: assets/site/images/

Front Pages' Theme:
HTML/PHP: application/views/front/theme_front.php
CSS/JS: assets/css/ + assets/js/ + bootstrap/
IMAGE: assets/images/

Sign Up Form: (sign up form is loaded into front theme)
HTML/PHP: application/views/page/sign_up.php
CSS: sign_up_page_layout/

Backend Theme:
HTML/PHP: application/views/admin/theme.php
CSS/JS: all css and js for back end are loaded in application/views/include/js_include_back.php and css_include_back.php

Go to css/skins/_all-skins.min.css and find the following css selectors and change background colour.
a)skin-blue .main-header .logo
b)skin-blue .main-header .logo:hover
c)skin-blue .main-header .navbar
d)skin-blue .main-header li.user-header