email validation input field

The biggest challenge for me was designing the correct behavior for the input field with a button and a pop-up error. At first, I tried to modify the default error for the input type email, but the only thing I managed to do was change the content of the message there, so I decided to create my own logic, which is quite complicatedly written, but it works. Any comments on what I could have written better/differently are welcome :)