You know what makes a senior dev? They've already made all possible mistakes and learned from them. You're on the right path.
I'm very senior these days. Most of my job appears to be unsticking people. But even I get stuck plenty, and while I can quickly unstick most problems the other devs face I can't solve all of them. Getting stuck still happens. The real difference between what I face now and early in my career is that I have developed a sense for when to plow through, when someone else might know the answer, and when to route around.…
Over time you start to develop a sort of automatic pattern recognition skill that separates problems to "I've never seen this before" and "oh, this looks very similar to x". Also it becomes much easier to know what's hard and what's easy, like you said.
You still obviously make the wrong call here and there. More often if you're in a completely new field, like the OP.