Completely new to WordPress

I had a wordpress website built by some international uni students. Unfortunately, now that I am ready to utilise the site the students have returned overseas and I have no contact with them. I have no idea how to maintain and fix the website. I did not receive a user guide or operating instructions. The holiday rentals calendar / booking site does not work. I am a start up business with limited funds hence why the site was built by uni students for me.

The page I need help with: [log in to see the link]