> I have no probs reading and listen in english, but writing is bad caused lack of practice.

It's worse than my German, and I have the excuse of German having lots of cases and inflections (but fewer than Russian). English is like a toddler language in comparison ;)

Best of luck with your English practice.

Put some text about the "source code sources" in your docs. Just take what you wrote in the comments here.

Same goes for the redirector/DOS versions.

Structs are essential to good, clean coding in C (and most other languages). Modern compilers are good at handling structs being passed in and returned from functions, especially for small inlined functions. They are also good at handling pointers to structs being passed into functions, especially for small inlined functions. Play around with gcc/clang + either the -S option (to generate assembly output and then stop) or with objdump or some other assembler. Or use godbolt (Compiler Explorer). You'll be amazed at how efficient the code is.

It's probably a good idea to create a number of short instruction traces, maybe just a thousand instructions each, and figure out a way to build a program that runs them and times each of them. If you can also enable profiling on your Raspberry Pi Pico target so you can see where each trace spent most of its time, it would likely be very useful.

What's your roadmap for the project? Just tinkering? Becoming a better C programmer? Becoming better at embedded programming? Better at ARM32? "Quality of life" improvements that make it easier to use the emulator? Better emulation? Specific games/apps you want to work well?