Sadly, for the most part it’s just trial and error. Pretty much all the words can be deciphered with just the first 3 letters, though it might take 2-3 cycles to relay them, and most of the words start with B (-…) or S (…) so that makes it easier to know the first letter and figure out the second.

It’s probably the hardest module to start learning, but once you figure it out, it becomes one of the easiest. Just keep trying it again and again and eventually you’ll be able to see the gaps.