It's a first game with kobolts that don't make DM and players get bored. Maybe too much normal kobolds I recommend to add on strong or average a Kobold Dragonshield instead 4-5 normal kobolds. History in this game is interesting and it is reasonable.

Nice crawl. But it is a little complicated to make this doors work and don't kill 1st lev characters. It's a pity that autors say nothing about chitines.

Ghost as an encounter is not a good idea, especially that it is hard to calculate the time when the players see Matthew. Moreover, the curse is disgusting ;/ If you have characters that would level up into 2nd tier after this adventure you basically make it so they have to have this curse for the rest of thier adventures, which is not a good adventure design. The high-DC throw for realizing that you are in an ancient city makes no sense whatsoever, especially if you played the first part, as you are constantly remainded of that fact. The cave fisher encounter, on the other hand, is great, but that is one of the few things that is good about this adventure.

Cool adventure. If you want to make grungs encounter more funny use volo variant for poison. Nice balance between combat and roleplay.