Little help with "finishing a level"

well hello guys, i’m working a sort of 25d side scroll game and while i’m already know how to do most of the game mechanics still have some stuffs which i would love to have some help:

1 - a dialog start- like megaman and others 2d games, i want at the start of the level to appear a dialog between the main character and a support character, while i do know how to “disable inputs” make a delay and enable again after the delay, the issue is the Dialog itself, anyone know a tutorial about how to make a "start level dialog?? or can give me some hints/help on how to do it:

What i want is at the start of the game the character will appear like was teleported then a small panel with a dialog between the characters appear then you can “click” to speed up or wait the dialogue to go alone then after they finish the character can move;

i do know about make widget but not know how to make this sort of “control” to make it display different texts, have for each character speaking s proper portrait, it will be the “same” dialogue box where both will talk in turns the talk will go naturally like character A talk then after it finish talk like 2 seconds after the second one start replacing both photo and dialogue from the A to B then it’s talk then after it finish then 2 seconds later A talk again then it’s go until all dialogue ends

then after they end talk the player can get control over the character and start to play.

second is the related to the topic

2 - how you can "end a level after kill the boss - the level will have a “final boss” then after you kill it another dialogue appear between 2 character then after that the game "display a “thanks for play” and a “credits scene” then after that it go back to the main menu, how i do that “call” after kill the boss, while i do know how to make the thanks for player and credits i just don’t know how to “hook” it to the boss death.

any help on those 2 questions is very wellcome.

1.Yon can create the binding of the text.
2.Get the health of the boss and if it is ==0 then do the speech,credits etc

hmmm ok i will give a try, thanks for the help