I can edit the default "Contacts form"?

Under the /templates/hot_restaurant/html folder, I only see the following folders

mod_search
mod_menu
mod_breadcrumbs

Then you are probably using j1.6/j1.7 and we do not have layout overrides for that version of template. If you relay need something taht can not be done using default j1.6/j1.7 contact template, you can use some 3-rd party component or create layout override yourself.

i tried to filled the contact form and sent it, but i don't know where the message going.. how we can set the email address to receive the message sent from the contact form?

Go to the Contact component and edit default contact that's already there (after HotStart installation). Also, check if in Global configuration your email settings are correct. Also, check if super administrator's email address is correct.

can i add calendar into the contact form?

and how to add more required field text?

you need to customize contact form from code. Calendar does not exist at all.