how long before the 1st scene on map i didnt kill the 1st boss with 10flr to clear yet?
The first scene, I'm certain, is completely randomly found at any one location on the map during Evening. Immediately after the first failed attempt to clear the dungeon the first scene is available but you have to find it, there's no indicators as to where that location is.
I recommend saving the game immediately after intentionally failing the dungeon (in the decontamination room) and then go roaming around to search for it. Unfortunately you do have to search not just the open world(s) of the map but also inside of each and every building including rooms inside of the buildings to find the scenes.
It's important to note that also unfortunately there is a sort of "Time Limit" to finding these scenes, as it can transition from Evening to Night without prior notice, but there is at least one indicator that lets you know when that "Time Limit" is up. The "Timer" depends on how often you've been in and out of places transitioning between maps etc. You'll know you've missed the opportunity to trigger a scenes events when speech bubbles pop up in the lower left corner of the game. This goes the same way for Night events too, except for when you miss Night events as soon as you see those text bubbles pop up on the bottom left of the screen it means you missed the chance to get the Night event to trigger and would have to go to bed and fail the dungeon again to try it over again. But that's why I tell you I recommend saving the game immediately after failing the dungeon and you're in the Decontamination Room.
This gives you the chance to systematically check and mark off every location on the map and each & every room in every building you can remember to check off the list of places to check. Once the speech bubbles pop up, you've missed the chance to find a trigger-able event, so go back to the games title screen and load up your last save and resume your search from where you left off.
I recommend saving two times -- once in the Evening for searching for the Evening Event Trigger, and another save for once you've found that Evening Event Trigger so you don't have to repeat the Evening scene over again just to roam around looking for the Night Event Trigger.
It's a pain in the ass, I know, but it's the best method I had to figure out for myself. There is no indicator telling you where or when an Event Trigger pops up.
The only thing to note I can think of beyond that is that if you find zero Event Triggers on both the Evening and Night cycles, it means you have to progress in the dungeon and defeat a Floor Stratum Boss. That's about all I've figured out on my own from this game so far.
