Hi Bnisbet,
I can certainly understand the frustration! I think it’s common with any large piece of software that you would come across. I would consider myself very proficient with 3Ds , but there is still a lot of things within it that I am continually learning to improve my workflow and process! I don’t think that will ever change. It’s a little unrealistic to think you’ll pick up and learn everything within any software that is as vast as UE4 or for me 3Ds .
If you’re wanting to focus on level design my advice would be to learn the things that are most related to that, such as using the Landscape tools, FBX importing, 3D modeling, the foliage tools, Lighting and it’s different types, and so on.
I personally find it’s best to not overwhelm myself with learning everything and to focus on “What do I need to know to do this one specific thing I want to do?” For example, if I wanted to setup god rays to shine through a window I would research and see what documentation is available for this. How is it being used in the engine? Is it using fog volume and lighting to cast the god ray or is it being faked by using a material and static mesh? These are the types of questions I would consider. Then I would look at the performance overhead of both and see what’s going to fit the style of game I want to create.
Luckily for you, there are many many video tutorials and documentation available that Epic has made and that the community have made as well! We also have a great staff here at Epic and a community that is willing to help individuals like yourself learn! 
Below are some links to information and tutorials that you have missed:
Epic’s YouTube Video Tutorials
Unreal News Weekly: Community updated list of tutorials provided by different users and their descriptions
Trello UE4 Roadmap: In the videos section you can see when specific tutorials and documentation will be tentatively provided by Epic.
Docs.UnrealEngine: This is a great resource simply because when you search it will search AnswerHub, The Wiki, The Forums, and API. You can search through these individually or all together!
AnswerHub: This is a great place to ask more specific questions if you’re having trouble. Even searching you may find answers to questions where you were running into a roadblock.
I wish you the best of luck and if you give it a chance you will see how rewarding and powerful this engine is at creating something spectacular. It will take effort and a lot of banging your head against a wall to figure some things out but knowing that you created something cool that others can play will make all that frustration just fade away!
If you have questions or need specifics feel free to ask!