This is part of starting off.  You’ll be copying a lot, second guessing your work and bewildered your code actually works.  Seasoned programmers still end up in situations like this.  The industry changes so fast a HUGE part of coding is barely grasping what your working with and still pushing you skills further.  

Keep going through tutorials, try to slowly hand code things rather than copy/pasting(libraries and copy/paste is a huge part of coding big projects) and realize this is a skill that can take decades to truly master.  For someone only 3 weeks into it the code you created looks amazing.  Keep it up!