Script in JavaScript

I am interested in writing a script in JavaScript.

The essence of the script is a pop-up window from several slides, which will pop up either when you open the page, or when you click on a certain button or area of the site, or when a visitor leaves the site (the idea of tracking this action is already there, but first I will listen to your options).

There will be 2-3 slides for each window.

With each type of display, all slides, except the last one, will have their texts and buttons continue or reject with different inscriptions. The last slide will have a form for entering contact details, a timer and a button to send. The editing should be through Ajax on PHP script (the PHP part is not necessary to write). After sending, a message about the successful sending should appear in the same window, and the countdown on the timer should also begin. After the timer is completed, 2 more buttons should appear that will send ping to a particular PHP script via Ajax.

The project described 80%. Wh. I want to hear the cost and time as close to the real as possible.