Create Dungeon or Find resources about Specific Absalom location

My players have gotten really into exploring Absalom, as one of the members happened to build a Knight of lastwall character after coming to absalom they are now working with Ulthin to clear the Precipice district.

I am wondering how to properly scale the threats they will experience. For example i threw some Swarms of insects from the stingers scar but forced them back without properly "clearing it" and now they want to explore the drownyard. Is there any way to create dungeons that are to their level so they clear them or is absalom/ precepice district designed so they explore only a bit at a time and get forced back for later after gaining allies and resources because it is so overun with curses.

Alongside that are there quick and easy resources to designing dungeons as i can build encounters fine but the dungeon building is brand new to me.