I would like to add a contact form like you have, http://mago.magento2.demo.ubertheme.com/contact/
I’ll add mine here: https://designerfabricsusa.com/contact-us
The documentation you have for https://www.ubertheme.com/docs/ub-trex-pro/#contact_us does not exist in the UB Mago themehelper.
Do you have instructions?
Also, your Magento 1 theme version had a Get a Quote form in a modal popup, does this theme have that?
I see now it is the Magento default, described here: https://docs.magento.com/m2/ce/user_guide/stores/contact-us.html
It’s true that we used default Magento for the contact form. Please follow the Magento guideline like you mentioned above to set up your way.
In case you have any additional question, please get back to us here.