How to store display value into a variable

I’m having a tough time figuring out how to store my display value in a variable so I can store the first input value into a variable every time I hit an operator. Also, if anyone could shed some light on how to create another string once the operator has been pressed that would be greatly appreciated.
Here’s my github link to my code: https://github.com/silashuereca/Calculator

Thanks to anyone in advance

-Silas

I actually figured it out! Thanks for getting back with me so fast though!