Bests & Worsts Reviews from Amazon

I tried this from the Google store and uninstalled after four days. I had horrendous lags on the phone, whether I was using the Amazon app or not. Uninstalled it, everything went back smooth. Installed it today from Amazon store, phone is lagging again. Other than the fact that the phone slows down, WHAT IS AMAZON DOING IN THE BACKGROUND? If the app is affecting performance, how much data is it collecting? There are a few other small annoyances, for example I get notification on an app upgrade available. I decide not to upgrade due to new permissions. I get the notification again every day. On a side note - why is Amazon putting a few app as the free app of the day?