Thank you trying out the game, and for the very detailed feedback.
Tutorials are my greatest weakness right now, and I think the only solution will be to add button prompts to all menus. I've actually already made a map this week because you are not the first person to bring that up.
The journal is indeed totally broken.
You can't equip weapons from the inventory, only from the stats / equipment screen so that was't a bug either.
If you want to know how to continue: Katrina should've said to visit Mosca after sending the letter, and then she gives you another quest, and upon finishing that one the sun will set and Modest will be waiting for you behind the chapel.
Nevertheless, it's crucial for me to know if people are getting lost so I earnestly thank your for the feedback.
Thanks again for playing.