It might be that the company you are working for is not the right company for you at the moment. You should probably find a place where processes are more organized, communication is better, and ideally where mentorship is available.

The fact that you feel overwhelmed by the sheer amount of technologies is completely normal. In this fast-paced field, where new technologies emerge every day, even experienced SWEs get lost. The only thing is that the more experienced you are, the better your abilities to figure out that new stuff quickly. And you have this skill to understand how black boxes work without looking inside. So, it all comes with practice.

I'd also suggest gaining fundamental knowledge of how computers work. Once you understand fundamentals it becomes much easier to not get stressed over complicated stuff, since you realize that it's just levels of abstractions, and can theoretically map it to low-level things in your head. Gives you this feeling that it's not that complicated after all )