Greetings milansab and welcome to the Avast Forums!
Like alan1998, I also did some checking on your parked domain site. The only thing I found which MAY have something to do with the negative Avast rating, is in a reverse DNS lookup, I saw information indicating that at least twice in the past 3 years, your IP was evidently associated with malware.
Since this occurred before you acquired the website, the Avast team should be able to readily sort everything out.
(As they tend to be rather busy, it may take a little time for them to complete their analysis, but rest assured...they will get back with you about your ticket).
Best regards,