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!