actually understanding the code?

(this post seemed to fit better here than helpdesk)

So even after implementing allot of tutorials, from very basic one line changes to replacing the weapon system, before my hiatus. 

And recently after implementing a few more including the switch activated pwalls, and watching hours of videos on Programming Concepts and C++, I still only very vaguely "understand" what I am looking at in the Wolfenstein source code. 

I think I have made some very basic level progress in understanding the most basic aspects of the wolf code but as far as understanding what I don't understand I cant effectively articulate it, other than once a line of code gets too complex or works with code a few other places, I am in the realm of grasping out of my reach of comprehension, as well when I see an operator used in place it seems counter intuitive I often don't fully get it, even sometimes after I look up that functions origin to grasp it. 

There are times when I think I understand what is going on, but once I start messing with it.... I often end up with errors or code that does not do what I intend it to, and get stuck for days on end. Like trying something seemingly simple as to create a key locked switch.   [mostly working now... and the problem was something small  ]

Does anyone have some advice on how to actually comprehend the Wolf Code, in a way that I can write my own code changes? 
Much of what is left to be changed in the KSS series engine is beyond the tutorials on the forums, and I don't want to be that pesky person asking too many questions. 
I'd like to put some of my own tuts on the forums eventually to give back.

In the mean time... [of my allotted free time] I am watching some videos on working with unfamiliar code bases.

I'm not sure yet what you're trying to do.  At Diehard Wolfers at http://dhw.wolfenstein3d.com/ , there's SDL Code Crackers, Code Crackers, and Code Tutorials subforums.

well in short words, I'm trying to understand the Wolfenstein source code, so that I know what I am looking at in the code, and so that I can write my own changes.

Switches and weapons code are the WORST, nobody really understands them, and just when they think they got their head wrapped around all that disorganized stupidity they forget everything a few months later and their game is full of switch and weapon related bugs. Run far away from those two things while you still can.... and from wl_menu

Well I don't think my weapons code has any bugs in it, I've tested it as extensively as I know how to and haven't encountered anything wrong. 
And the switches are also pretty crucial to secrets of KSS, and a significant portion of the gameplay. Actually I think I'm just a few basic steps from getting the switch system to function as intended. I just dont understand the system of how door locks and keys work. To make the a locked switch that checks for ___ key. 

But getting stuck on something so seemingly simple as that, I am wary to attempt to implement my more brutal take damage system.

I think as much as I dread it... I'm just going to have to actually work through creating the boring console applications that are common in the C++ course videos on YT. 
And when my new phone arrives, I will install the C++ learning app I was using before my hiatus, I think I remember it helping, and I think it was a paid pro app.

Well I got the key activated switches working, and as I suspected I wasn't so far off, but was testing on a further down set of switches&pwalls that seem broken. 

After I have sorted out the issues I may post a tutorial, but it is really just a more complex version of Brother Tanks Switch activated pushwall tutorial(so credit to BT), that uses several different sets of switches and pwalls, that add some versatility to it. There are still some things left to sort out too.

Regardless, I have a whole swath yet to learn.... vast swaths of.. code... 
I'm not going to say I understand this code until I can open up any given file of ye olde wolfsrc and understand 7 of 10 lines of code I happen upon.