Can You Please Help Me With This Code?

Question

So, I just started to learn C# just the other day. I made a calculator code just for fun and so far, it only has addition and subtraction and a bug. Could you please tell me where I messed up or if it is just the bad compiler on the phone? Thank you!
Link:
https://code.sololearn.com/ceC2j7Tif81v/?ref=app

Answer 1

What's wrong with it? It works fine on my phone.