Is it supposed to be the best free anti virus program?
You aren't really asking this question in the best place for a neutral answer. Not many people on the avast forum are likely to suggest that a.n. other free av is much better - if they thought that they would be using it and wouldn't be posting here.
It has a good reputation for resource useage and usually scores very well in independent tests.
Only you can decide if it is the best or if you should continue using it.
What do you mean by all the red pop-ups? Detection alerts?
If so, then unless you keep deliberately visiting the same dodgy sites it may suggest that you have some rmalware (redirect or similar)