Intro Page Help

So I have a wordpress installed in a root of my website for example mywebsite.com and I am trying to get it so that I could have an Intro Page as my Main Page for this I will need to move wordpress site to mywebsite.com/site/ and have an intro page I made to be in the main root directory on mywebsite.com/

I followed this instructions (Giving WordPress Its Own Directory) What I found here is that once I finished the steps all I did was really move the wp-admin section to mywebsite.com/site/wp-admin and whenever I go to mywebsite.com/ it would point to the same root directory and not to the mywebsite.com/site/ directory (that i know of).

So at this stage if I visit mywebsite.com/site I just get “HTTP Error 500” I thought that if I did this process I would have the site running in a sub directory mywebsite.com/site which is what I want instead I just have the wp-admin running in a mywebsite.com/site/wp-admin.

Anyways if there is a way can someone please help me out a bit and point me to the right direction on what am trying to do.

I eventually would just like to have a Intro Page or AKA a Splash Page to be in my root directory mywebsite.com/ and when the splash or intro page is finished playing to go to the wordpress site that would be in mywebsite.com/site

Thanks!