The Contact Owner button from single listing page can be removed with css.

#contact_host {
display: none;
}

.owner-page-wrapper #contact_me_long {
display: none;
}

#contact_me_long_owner {
display: none;
}

The guest dropdown from contact owner form can be removed with this css

#contact_owner_modal .form-control#booking_guest_no {
    display: none;
}

Check-in and check-out can be removed with this css

#contact_owner_modal .form-control#booking_from_date {
    display: none;
}

#contact_owner_modal .form-control#booking_to_date {
    display: none;
}

#contact_owner_modal .form-control#booking_to_date {
    display: none;
}