CMS development

Galera is the next. I need to develop a Web project, which uses a Content Management System (CMS). The idea of ​​an integrated university project is to create a website that creates another website, such as WIX. I have no trouble creating the site. in itself,
My question is: what technology or library should I use for this? I need a light to guide my research. I repeat that my difficulty is not to create the site itself, but to know what to use to repeat what WIX does.
thank you so much