working on project

i'm working on project were when player goes into a dungeon when you go in it detects the player and summons mobs in certain erias in radius of 5 you can either rush the dungeon or you can clear it it has boss room and tresure room boss whice requires golden nuget to open path to it you can get golden nuget from crates inside dungeon after completing boss you are sent back to loby how can i do it? i have no knowladge on datapacks thats why im asking for help