Why and how the text could be Bavarian

[ololololo]

Yes, I understand, but the question is about the algorithm as a whole, not this example. How easy is it to decipher, knowing the algorithm?

So far, it's pretty simple: Just find a space, look at the two letters to its right and left, find that bigram in the list below the text, and then replace it with the vowel next to it.

It gets more complicated later on—there are also different lists for the consonants, but I'll get to that soon. Overall, though, it’s not that easy if you don’t know the cipherer’s writing habits and dialect. That’s why I also think it’s a bad cipher. But more on that later.

Unfortunately, handwriting and dialect are problems for us, but not for the "recipient".
And at what point does the cipher become more complicated (the same consonant lists)? Is this observed in VMS?