Help for book your travel

Hi, I have a problem with my website …my webmaster done it 4/5 years ago with the themes book your travel…all works fine, just only it blocked all updates, and now, after I update wordpress from 3.7.1 to 4.9.5 , the theme not works, because I can’t update it. I had installed envato toolkit but I can’t update my theme cause was purchased from the webmaster who now missing and I can’t recover all dates required for update.

Pls can you help me?