Having said that, don’t sweat the details.
You’re not expected to design the thing from scratch.
Use any unofficial materials to understand the overview and not to study the details.
http://www.b737.org.uk/aircraftsystems.htm
https://m.youtube.com/@ChrisBrady737/videos
https://aviaforum.ams3.cdn.digitaloc...147668092a.pdf
There’s tons of other stuff out there.
Just heed the warning.