Thank you for your helpful response.
I wrote about not being able to learn assembly because I just wanted to avoid endless discussions assembly vs. high level languages. Yes, you are right, it is relatively easy to learn assembly. I taught myself the z80 variant (in the early eighties) and wrote screen compression routines (that even worked) for my ZX81 and later spectrum. However, as I've already said, this is just a hobby, and I am more interested in learning to communicate with the "outside world" (sensors and process controllers) then to become proficient in yet another version of "machine language" (as it was called long time ago). On top of this, I already "speak" Basic and C.
Thanks again.