Some Intro
A newgrad working as SDE-1 at Amazon, India for past 8 months. I have good WLB (30hrs per week to 45 hrs tops), team also does good work and I regularly get exposure to engineering advice from SDE-2s and SDE-3s in my team. Also, I get to attend lot of design discussions though I am not able to understand much :(

Situation
Owing to decent WLB, I spend most of my free time on CP platforms (10-15 hrs a week) since I like problem solving and it also makes me feel comfortable about my skills & prepared for any future opportunities. Though I like real engineering stuff a lot, but I just can't figure out how to start. Resources for system design are so scattered and almost no-blog or course provides a good bottom-up approach (from basic to advanced stuff).

Doubts
So here are couple of doubts I have for which I need advice from experienced folks:

1. Am I spending too much time on problem solving? Is it fine if I just continue with it or is it just a waste of time that could be used somewhere better?
2. What resource (preferably books and engineering blogs) do you suggest for gaining system designing and engineering skills? Consider that I am not in any kind-of rush since I am anyways not looking to switch and have decent amount of free time to utilise. I have heard DDIA is excellent, but I don't know if it's begineer friendly.

Any help regrading this would be extremely useful and much appreciated!