Is anyone can expllain managerial accounting chapter 4 and 5 please. I don't get it at all

We don't know what your chapters 4 & 5 are. Also not quite sure why process costing should be taking up two chapters.

And no, really, no one could possibly explain equivalent units in some post on a forum like this. Well, it's not literally impossible, but would be a mile long, take a very long time, and be very difficult to do. In other words, we'd just be writing your chapters over again, without some kind of hint as to what exactly you aren't understanding. -- so for all intents and purposes, impossible.

You really are going to have to ask specific questions. If we at least knew something specific, we could explain just that part.

I can give you a link to process costing:
Principles of Accounting Chapter 20