editing the login way of wordpress website

I have a wordpress website have hestia theme which has a frontpage page that contains a button that leads the customer to the "order" page. What I want you to do is to edit the button function, 1-If the customer has already an account in the website but he did not login. After clicking on the button, two fields appear in the same page and two button without redirecting him to another ,First field is the username(@) and the second for a password. The first button for login and the othe for those who doesn't have an account "sign up here". Clicking on sign up will show extra 2 fields, one is for the mobile number and the other is for the city of the customer. Note: after registeration or signing in the customer will be redirected to the order page. 2-If the customer had an account and he already logged in the website: clicking on the button will redirect him to the order page . Note: the username is the Email of the customer.