@ Jeronim0
Here is why the standard shield didn't detect anything initially.
Archive (zip, rar, etc.) files are by their nature are inert, you need to extract the files and then you have to run them to be a threat. Long before that happens avast's Standard Shield should have scanned them and before an executable is run that is scanned.
So with the standard shield on the Normal sensitivity doesn't scan archive files by default as at that time they aren't an immediate risk.
With a view to the eicar test file again there are many types and like the above statement only those with an immediate, executable risk would be scanned by the standard shield (the web shield differs in that it scans 'all' http traffic), e.g. eicar.com and eicar.exe, etc. but not a zipped version of it nor non-executable file formats like eicar.txt.
However, you don't say what the file type was that you downloaded ?