WebApp connected to a Google Sheets model

For this project it is required knowledge on Google Sheets, Google App Script and HTML, JavaScript and CSS code.

I want to develop a Web App backed in a Google Sheet and I need a developper able to write HTML and CSS to give shape to the script.
The operations are like following:
- The users can fill some fields in a form-like view or import them from a Google Sheets with a button
- With a submit-button:
(1) one of the fields is recorded in a Google Sheets to a model that will give an Input1
(2) the view will display a new area to fill with a message with the Input1
- This new view will include:
(1) Dynamic pre-filled information will appear depending on the user answers in the new displayed part
(2) Depending drop-downs
- Last button with a recording to a Google Sheets database and the automatic sending of an email & sms with the recorded information
I've attached the template for the Web App

I will give more details once we open the project.