What a kata.. why 5kyu? I believe this is at least level 4 being quite elaborate.
Also this one is much harder than Wordle (also and fairly decent 5kyu) which I cracked earlier.

for nerds only

The description is mediocre, could not "make head or tail" of the actual game rules

This one is more like a math problem, of course regex might help.

If it's the problem of not understand the description, please let me know.

What I mean is that comparing with others 5 and even 4 kyu katas this seems incredibly complicated. I'm not into regex, and this was my guess of missing smth. Otherwise I am clueless of how even to approach it

You're just supposed to solve the kata. How you will do it is up to you.

Am I supposed to use bloody regex here?

Way too tough for 5kyu. Suppose no 5kyu level would be able to crack it without looking into the solution on the web

goddam it is so hard to understand how it works, despite the code itself is rather simple..

Finally solved it, but had to briefly look up in the solutions at first. Good kata with a non-standard pattern and logic, compared to what I usually face here. I suggest specifying the details more granularly as at glance it is hard to figure out how the code should be designed for non-exp ones like me. And the kata itself is not so sophisticated, hence on the relevant kyu level this kata would come in for a lot of clarifications from contestants.

To be sure you understood correctly: one call of beep is equivalent to one -or . or ... It has to be able to differ in execution time each time its called based on the message in the buffer. The decoder will execute beep multiple times per message. The decoder will continue to call beepuntil one execution of beeptakes a very small (no) time to excecute. Then the times measured will be translated back into the message.

Thanks for clarifying. One last thing about beep to check if I cottoned on it.
So, in other words, this function should take no more no less time than to be able to decode the initial message, providing some kind of 'time pool'. And this pool will be exhausting once the function is called by a certain amount, so at the end of the day it should be drained down to 0.
Am I right?

Way too complex. Solutions are elegant though, but even reading them I still struggle with comprehension of how they actually work.

So first of all both functions dont need to return anything ^^. You are writing a class Morser.

add_to_buffer will add the message to the buffer of the Morser without returning anything.

beep is a bit more tricky to understand. After the buffer is filled, beep will be called multiple times. Each time its excecution time is measured. Based on that a Decoder class will recreate the initial message if possible.

TLDR
beep does not return anything but should take a certain amount of time at each excecution.

I'm kind of perplexed with this one, probably due to the slightly ambigious description.
There are two functions, though for me it's unclear what exactly the should return.
add_to_buffer as I understood should return encoded str. But what are the rules? Is it strict Morse translation (when spaces are required after each letter and big space is needed between two words) or a simplified one? Could you possibly specify?
beep - what should it return? Just an integer calculating the exact time (in ms) required to decode this message to human readable?