I have a very simple project where I’m trying to learn how to use modules in C++20:

I am new to C++ modules. Let’s say I am creating dll , and I don’t want my users to see implementation details of my class . How can I achieve this in C++ modules ? Mostly I am seeing examples over internet , implementing functions in the same file . Can I safely say , module interfaces are similar to header files & module implementation is similar to cpp file ?
Here is my example implementation , is this correct ? I am using visual studio 2022.

I decided to get familiar with C++20 features, starting with modules. While doing that, I would like to create a simple GUI application based on QT. But apart from modules support in Cmake being crude at best, I noticed some strange errors, which are obviously caused by usage of modules, though I have no idea where do they come from.