[Python] Don't know how to use methods created

I'm super new to Python and programming in general. I am following an example off of youtube on how to make a simple calculator but I wanted to add my ideas and functionalities. More or less I want to make it very versatile.

This is the part that is not working out for me. I don't know how to make it work using the two methods I created

def main():
while True:
Num1()
num1 = int.num1()
Num2()
num2 = int.num2()


# Executing the specified calculations with the 'Operation' function (row 13)
Operation(num1, num2)

# --> followed by another nested while asking if the user wants to make another calculation


I want the app to read everywhere that if the user types "exit" it will exit, even if it's asking for a number so I created 2 methods to do so because it wasn't working dealing with the loops and user input directly from main()

def Num1():
while True:
num1 = input("What is the first number? ")
if num1.isdigit():
break
elif num1 == 'exit':
print("Thank you using the SimpleCalculator. Bye!")
time.sleep(3)
exit()
else:
print("I don't understand. Please input a valid number")
continue

def Num2():

while True:
num2 = input("What is the second number? ")
if num2.isdigit():

break
elif num2 == "exit":
print("Thank you using the SimpleCalculator. Bye!")
time.sleep(3)
exit()
else:
print("I don't understand. Please input a valid number")
continue


The problem is that I get this error and I get it but I just don't know how to go about it.

Traceback (most recent call last):
File "C:/Users/Albert/PycharmProjects/HelloWorld - First Py'
Apps/SimpleCalculator.py", line 131, in <module>
main()
File "C:/Users/Albert/PycharmProjects/HelloWorld - First Py'
Apps/SimpleCalculator.py", line 109, in main
Operation(num1, num2)
NameError: name 'num1' is not defined

Continue reading...