Dynamic Form Menu

Hi

I am trying to make a form with a dynamic dropdown menu on a specific page in wordpress.
I have made some forms with the “Contact Form 7” plugin, but the plugin doesn’t support dynamic dropdown menus.
I managed to create a dynamic dropdown menu by following this guide. But I don’t know how to apply this script on a specific wordpress page

The goal is to make a contact form so when you chose 1 option from menu1
menu2 will add some options.

The final form will include other stuff too like filling in your name.

I also want the details of the form to be sent in an e-mail.

Is there another plugin that does this or does it have to be done manually?
If yes, can someone help me with it? I’m fairly new to php and js.