Hi,
Kan (guy with glasses) has a chance to check up on Yuna, if that happens you have some time to hide under the bet - using arrows to adjust the view on the left side of the screen go down twice and then at the bottom of the screen you should see a 'ninja' icon.
As for flies, once it spawns, you should see a swatter icon in the same place as the ninja one and you just have to tap the fly. To make it easier, I suggest buying 'bug spray' consumable from the shop.
As for the night ending too fast, check up your stamina before starting the night, as it is the camera battery as well.
Hope this helps,
Cheers