How to update the project on SkeekS CMS 3 to version 5?

There are a large number of sites that run on SkeekS CMS version 3, although the last release of the 3rd branch is 3.2.3 - March 15, 2017, 0:50:37 (2 years ago). It was worth it before, but as they say "better late than never," I post an example of updating the site to the version of SkeekS CMS 5.