I really enjoyed the drama Alchemy of Souls, but it left many questions behind

The drama itself is so much fun that it's enjoyable even when rewatching.
However, the production process was quite turbulent, which affected the quality of the drama, and that's a bit disappointing.
Even without knowing the details of the production process, watching the drama left me with so many questions that I can guess it went through some difficulties.
First of all, it is divided into Part 1 and Part 2; Part 1 is a rare long-form series of 20 episodes for today's standards.
Part 2 is only 10 episodes, which is shorter than usual.
This imbalance is strange, making the latter half of Part 1 feel a bit dragged out, and Part 2 feel like it couldn't fully tell its story.
More than that, I wonder why they even made Part 2 in the first place.
Why bother making it by forcing a plot point about the female lead's face changing, when the story was already concluded in Part 1?
And more importantly, why did they make the ending of Part 1 such a mess and drive everything into catastrophe?
Now that I've seen Part 2, I feel like the ending of Part 1 had to be forced into that catastrophe just to make the second part possible.