Hello. I downloaded Avast Premier 30 day trial and now i want to switch to free version . What can i do please ? I don’t want this Trial anymore . I’m a little bit scared that i have to pay something after the trial expire. Please help 
You could go to Control Panel/Programs and Features and Uninstall the Version, then download the latest Free version and install it.
But if i will uninstall it , then after 30 days when the trial expire i have to pay something ? Or i just uninstall it and that’s it im over with the Premier Trial version and i don’t have to do anything special?
What about Virus Chest ? Viruses will be released back in my PC or it will delete them automatically?
Once you uninstall the Premier Trial version, you don’t have to do anything special; you are done with the Premier version period.
Virus Chest is deleted automatically when you uninstall Avast. Avast will not release the Virus Chest contents unless you manually tell Avast to. You will be safe.