Wordpress integration

Hi,

i've searched, but i find only similar posts that don't solve my problem.

I've a website in Codeigniter. Now, i want to add some page made with wordpress, for example a homepage and a contact page (i'd like to use wordpress because these pages will be make by my collegues that know perfectly wordpress).
How can i have some page in CI and others in WP ? 

For example, i need:

http://mysitename.com => show WP homepage
http://mysitename.com/animals/cat => call "cat" function of "animals" controller in CI
http://mysitename.com/contact => show WP contact page

I tried to follow this guide: https://www.cometchat.com/blog/how-to-in...wordpress/

But this didn't resolve the problem. Infact, to show WP homepage i've to go in the WP subdirectory.. something like: http://mysitename.com/wordpress and i want avoid to show subdirectory in url.

Thank you in advace and sorry if my english is not so good