Edit website with CMS

[Aleksey]

I am currently working on a website project and want to edit some parts of my website (news section and product page photos) with cms. I finished beginners javascript and php courses.My questions are:

1) Is it necessary to finish Begginers "Build a CMS project" first before start using some open source cms ?

2) Should cms be added from the very beginning of web design (because i already made main page and another one with html and css)?

3) Does anyone knows about some good tutorial out there? Because when i was searching for Wordpress tutorial, everybody just talks about making new theme. I dont need that just simple editing capabilities with cms.

 

I am hoping to get some answers because  i stopped working on my website project because its cms needs.