The app does not keep shapes when I put it in full screen - kivy

Question

I'm working on a kivy app. And I want to keep shapes once I put the app in fullscreen. When I launch the app, the screen is in mobile format. But when I put it in fullscreen, the taskbar shifts to the left and the text wallpaper and buttons don't stretch. Here is my python file:
from kivy.app import App
from kivy.lang import Builder
from kivy.uix.widget import Widget
from kivy.core.window import Window
Window.size=(480,720)
class MainInterface(Widget):
def A_pressing(self, s_img, SM):
if(SM.current=="background_2" or SM.current=="background_3" or SM.current=="background_4"):
SM.transition.direction= "right"
SM.current="background_1"
def PRD_pressing(self, s_img, SM):
if (SM.current == "background_3" or SM.current=="background_4"):
SM.transition.direction = "right"
if (SM.current == "background_1"):
SM.transition.direction = "left"
SM.current = "background_2"
def SI_pressing(self, s_img, SM):
if (SM.current == "background_4"):
SM.transition.direction = "right"
if (SM.current == "background_1" or SM.current == "background_2"):
SM.transition.direction = "left"
SM.current = "background_3"
def SO_pressing(self, s_img, SM):
if (SM.current == "background_1" or SM.current == "background_2" or SM.current == "background_3"):
SM.transition.direction = "left"
SM.current = "background_4"
class CustomApp(App):
def build(self):
sm = Builder.load_file("main.kv")
return sm
CustomApp().run()
And here is my kivy language file:
#:import utils kivy.utils
MainInterface:
<MainInterface>:
ScreenManager:
id: sm
size: dp(root.width), dp(root.height)
Screen:
name: "background_1"
Image:
source: ".\control_bar_images\Background_1.png"
BoxLayout:
pos: dp(5), dp(71)
size_hint: (1, .70)
padding: 18
opacity: 0.8
canvas:
Color:
rgb: utils.get_color_from_hex('#BDBDBD')
Rectangle:
pos: dp(0), dp(70)
size: self.size
orientation: 'horizontal'
ScrollView:
# take half of parents size
size_hint: .5, 1
pos: dp(0), dp(-20)
Label:
canvas.before:
Color:
rgba: 1, 1, 1, 0
Rectangle:
size: self.size
pos: dp(0), dp(-20)
markup: True
halign: "justify"
text: """[size=19]Lorem Ipsum[/size]\n\n[size=14]Neque porro quisquam est qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit...[/size]\n\n[size=18]Lorem[/size]\n\n[size=16]Lorem ipsum dolor sit amet[/size]\n\n[size=14]Lorem ipsum dolor sit amet[/size]"""
color: utils.get_color_from_hex('#FFFFFF')
pos: dp(0), dp(-20)
size_hint: 1, None
text_size: self.width, None
height: self.texture_size[1]
Image:
source: ".\control_bar_images\Top_Bar_4.png"
size: 480, 135
pos: 0, root.height-135
Button:
size: 112.5, 75
pos: root.width/2-205.75, root.height-100
background_color: 1, 1, 1, 0
on_press: root.A_pressing(A_img, sm)
Image:
id: A_img
size: 112.5, 75
source: ".\control_bar_images\image_about.png"
center_x: self.parent.center_x
center_y: self.parent.center_y
Button:
size: 112.5, 75
pos: root.width/2-110.25, root.height-100
background_color: 1, 1, 1, 0
on_press: root.PRD_pressing(PRD_img, sm)
Image:
id: PRD_img
size: 112.5, 75
source: ".\control_bar_images\Likes_Btn.png"
center_x: self.parent.center_x
center_y: self.parent.center_y
Button:
size: 112.5, 75
pos: root.width/2-12.75, root.height-100
background_color: 1, 1, 1, 0
on_press: root.SI_pressing(SI_img, sm)
Image:
id: SI_img
size: 112.5, 75
source: ".\control_bar_images\Start_Btn.png"
center_x: self.parent.center_x
center_y: self.parent.center_y
Button:
size: 112.5, 75
pos: root.width/2+78.75, root.height-100
background_color: 1, 1, 1, 0
on_press: root.SO_pressing(SO_img, sm)
Image:
id: SO_img
size: 112.5, 75
background_color: 1, 1, 1, 0
source: ".\control_bar_images\Stats_Btn.png"
center_x: self.parent.center_x
center_y: self.parent.center_y
Once I launch the app, the screen looks like this:
And when I put it in full screen, the screen becomes like this:
What should I do ?