Hackers into our site

Somebody from this 125.234.97.222 hacked into my website and is sending emails from our website.
And the same person is sending virus and other bad stuff to millions of people
I am very new here, can a good man/woman help me
We are a small NGO helping poor people . How can this person be this wicked to us.We do not even have resources to get another web site or move from the host
our website is
www,chistre.com
I need help from kind-hearted person
please help us

Go to IP > Firewall, add a rule to block 125.234.97.222

Chain = Forward
SRC Address = 125.234.97.222
Action = Drop

But ultimately configure better passwords on your website.