Branching dialogue in minecraft using a player scoreboard, a trigger, tellraw, and a command block chain?
You set dialoguetrigger to -1 and then immediately check for various values. It will only ever be -1 and only the command that checks for -1 will execute.
Scoreboard initialisation (creation, setdisplay, initial values) should usually only be done once in the process of making a map and not be put into a command block. Or you can have one place that initialises everything, but that should only run when the map is started, not many times while playing it.