from tkinter import *
import subprocess
root = Tk()
root.geometry("900x500")
def vs():
    subprocess.call("GUI.py", shell=True)

Label(root, text="Schere,   Stein,    Papier", font=("times",30)).grid(column=3)
Label(root, text="Menü", font=("times", 30)).grid(row=1, column=3)
Button(root, text="1 VS 1", command=vs, font=("times", 30)).grid()

root.mainloop()