Raptorkillz again, stop using chatGPT. this is something very simple and you are not learning anything from it.
chatGPT spews shit, and the process of making chatGPT code work is akin to polishing a turd.
I told you how to do this in one of the first posts, here's an even easier solution, but you have go and use your own "human hands", not wait for magic solutions.
1 - create a VBoxContainer, make it as big as it needs to be to accommodate the number of buttons.
2 - put your buttons in there
3 - try shifting the buttons horizontal position inside the VBoxContainer
4 - set next and previous buttons for each button

5 - to add animation, on each button, connect the focus_entered and focus_exited signal through code and play an animation with a tween
func _ready() -> void:
focus_entered.connect(selected)
focus_exited.connect(unselected)
func selected() -> void:
var tween : Tween = create_tween()
tween.tween_property(self, "scale", Vector2(1.1, 1.1), 0.1)#change size, or whatever animation you want
func unselected() -> void:
var tween : Tween = create_tween()
tween.tween_property(self, "scale", Vector2(1.0, 1.0), 0.1)#reset size
and then you would have to setup a theme to change the button focused, hover, pressed, etc visuals for your buttons.
for more complex animations like that shadow, you would have to add more nodes to each button, make them scenes and use the tweens to hide/unhide the shadow.
tweens can also be use to start or stop a loop of color change.