IF you need tutorials, remember that XNA applies a swell and it doesn't matter if it's 10 years old. But if you have been doing this for awhile then focus on general game dev information. A lot of good resources are written in c++ and are not about monogame. One of my favorite resources is http://gameprogrammingpatterns.com/ . It has a free web version.
Keep in mind that monogame is a frame work and it handles all of the low level stuff but you still are creating an engine. I really enjoy https://www.amazon.com/Engine-Architecture-Third-Jason-Gregory-dp-1138035459/dp/1138035459/ref=mt_hardcover?_encoding=UTF8&me=&qid=1557547565
This is my current favorite
But in the end, it comes down to any job. You reach a problem and search for a way to solve it.
Disclaimer, I haven't personally built a full functioning game engine from scratch but I've been interested in game engine architecture. I recommend two books I'm currently reading, Game Engine Architecture and Game Coding Complete.