Help! My web-developer dissapeared…

An acquaintance made our website for us, arranged web hosting and provided us with the wp-login.php login details.
Now that we want to change some of the content we don’t seem to have access to the main/home page of our site (all other pages we seems to be able to change)… We have been trying to get into contact with him but no response at all!!
Can anyone please help m e in the right direction so we can have full control over our site?

Thank you soooo much!!

Ps. the site seems to have the Arras theme