Will Custom page in WordPress be Responsive?

We have a situation where the customer is converting to a WordPress site. We have a custom part of their old site that is php / MySQL. We are currently unable to get that portion to function responsively.

You can view the current (non-responsive) page at www.rainrich.com/scheduling/indexwp.php.

My thought is to build few custom pages in Word Press, these pages being mainly the custom php & some text, as illustrated on the referenced url.

The question is, will these custom pages be responsive built this way using the responsive theme Avada?

Thanks