As a user I want to be alerted if i fill in invalid values to the fields before I click on the Submit field button - especially on the required contact fields.

Let's discuss what level of client side validation do we want to offer on the form fields. Currently we only have validation on the email field only and only when clicking on the Submit button. The two most important fields are the email and the phone fields so we should make sure that entries contain as little errors as possible. I would explore what can we add in no more than a few hours of development, starting maybe from here:

https://developers.google.com/web/fundamentals/design-and-ux/input/forms/?hl=en#provide_real-time_validation

or https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/HTML5/Constraint_validation

I'd also discuss how complicated it is to show "real-time" feedback on correct or incorrect entries as it can be seen in this example: https://secure.greenpeace.org.uk/page/s/no-new-oil

(though this lets you enter letters in the phone number field)