I have gone through the book "Mastering Bitcoin" and I am not able to completely  grasp  it.  I just need a break from reading and need to do something practical.

Is "https://github.com/bitcoin/bitcoin/" is the original copy?
How  should I  read the source  code?
Do I need to install some specific program /compilers  for it.

Edit.
My ultimate goal is to become Blockchain developer.
I am a software engineer,BS or BE or B-Tech degree holder in computer science field. So I read the programming language and Data structures in my college life.

Now Bad part:
Even today I work as software engineer but never used programming skills, so whatever I read is almost 15 year back in life.
In job , I worked as ETL developer/tester (A gui tool ) so no programming language after wards I transitioned to Performance DBA (Work on tuning of Database 150+  tearabytes in size).

I downloaded github also (as a zip file) , but I did not find any directory till now where I can find C code.

Actually I want a transition in my job field by learning a new skill. Actually if I learn the blockchain skill, there is high probability that I can move to another project of my company that is doing blockchain but I need to acquire skills first.