Understanding programs architecture in C++

I have studied GOF and GRASP patterns, remember each of them well, and can easily write a code example with one of the patterns without hints. But when it comes to real projects, the maximum that comes to mind is a singleton pattern(which I use very often because I do not understand how to do otherwise better). After a few thousand lines of code I begin to realize that I make a lot of mistakes in the program's architecture and could have done better, even using the same design patterns. Somewhere I do not understand whether to create an Application class that will store objects of the Gui, Network classes, or better to make Gui and Network singleton. I understand that everything should come with experience, but after a month I understand that I did not understand how to do it correctly - and did not understand. Are there any good books that will help you better understand the architecture of programs? Or examples of open source projects with a competent architecture to understand what a good application architecture should look like? Thank you in advance!