Problems adding buttons into new window in tkinter python 3.6

Hello, I am new here, and this is my first question so excuse me for any possible mistakes

from tkinterimport *
import tkinteras tk
from tkinterimport messagebox

firstwindow = Tk()
#Creating my first window  
firstwindow.title(" this is my first window ")  

#Adding image to window
imagen = PhotoImage(file="imagen1.gif")
etiqueta = Label(firstwindow,image = imagen).place(x =370,y =75)

#Adding exit button and title button  
button1 = tk.Button(master = firstwindow,text =" DISCLAIMER ",font=('Arial',18,'bold'),height =3).pack(side = tk.TOP)
button2 = tk.Button(master = firstwindow,text ="exit",font=('Courier New',16),height =3,command =exit).pack(side = tk.BOTTOM)  
#Creating second window  
def create_secondwindow():
create_secondwindow1 = Tk()
create_secondwindow1.title("this is my new window!!!")

# Create button that will open second window  
button4 = tk.Button(master=firstwindow,text=" open new window ",font=('Courier New',16),command=create_secondwindow).pack(side=tk.BOTTOM)

#Trying to open a new message when using a button in second window  
def mensaje ():  
 tk.Button(master=create\_secondwindow, text=" Click here Ill give you a surprise! ", font=('Courier New', 16, "bold"), height=3, command=exit)  
 tk.Button.grid(row=370, column=70)  
 msg = messagebox.showinfo("Hello Python", "Hello World")  
 create\_secondwindow = Button(TOP, text="Hello", command=exit)  
 create\, y=50)  
#Open message button  
button5 = tk.Button(master=create\_secondwindow, text=" open message ", font=('Courier New', 16), command=mensaje).pack(side=tk.TOP)  
#Last exit button  
tk.Button(master=create\_secondwindow, text=" exit ", font=('Courier New', 16), command=exit).pack(side=tk.BOTTOM)  

I cannot manage to create buttons into the second window.

Thank you

try add ‘button5.pack()’. pack() method is comming from tcl/tk pack which packs a widget to the window. Defining a widget doesn’t mean it to be packed(displayed) yet