There already was a similar topic in the past:
The most important quote is this:
What this piece of code means is that you would need to press the “interact” action EXACTLY at the same time (down to a single frame) as the body entered the area, in order to emit the signal, which is close to impossible.
I would suggest you to rearrange your code to be the following:
var is_player_within_area: bool
func _on_body_entered(body: Node2D) -> void:
if body.name == "Player":
is_player_within_area = true
func _on_body_exited(body: Node2D) -> void:
if body.name == "Player":
is_player_within_area = false
func _unhandled_input(event: InputEvent) -> void:
if event.is_action_pressed("ui_accept") and is_player_within_area:
Dialogic.start("Wegweiser1")