Honestly, these lessons on sentence structures almost did me in, as do all grammar lessons--I'm far more comfortable teaching about the art of writing, and not the mechanics. The best I can do, I'm afraid, is to give you this link, which takes a fairly easy approach to complex and compound-complex sentences.
https://www.englishgrammar101.com/modul ... -sentences
I can probably answer specific questions, but I'm not sure that I'm qualified to give guidance on this from ground zero.
Sorry.

Jan Ackerson -- Follow me, friend me, give me a wave!
http://www.superioreditingservice.com
Twitter: @janackerson1
Instagram: janackerson
Facebook: Jan Worgul Ackerson, Superior Editing Service, Jan Ackerson, writer