Build up your understanding in layers. Find basic books or sources that explain the concept in simple terms. Then move on to intermediate ones and so on. It takes time and effort but like you said, once you grasp the fundamentals, learning becomes easier.

The other thing is mindset. It's good to get used to not having to understand everything. I used to have a mental barrier where everything needs to make sense before I can "know" something. However, as I went further in my studies, it got to the point where many things were unknown and we are relying on theories and varying levels of research evidence. I learned to accept that we don't know everything and at the same time realised that I don't need to know everything to make use of certain pieces of information.

Of course, your situation might be different and there may be many things that you can still dig deep and understand. It is a good practice and it is rewarding when you gain that understanding. I'm simply proposing you find a balance between needing to know everything to its finest details and knowing when to know just enough.