Sometime ago, i was having this difficulties of not been able to downliad applications from the google playstore. Whenever I want to download anything,
I will get an error 198 medsage meaning I can't download anything. Many Android phone users have encountered this problem one time or the other but now I will show you exactly what I did to get rid of this annoying situation. It will be a thing of the past once you follow these steps.

How Do I Get Rid Of Error 198 In Google Playstore?

1. Go to your phone and open settings on your Android device

2.Locate applications in the setting menu
3.Tap application manager
4.Select Google Play Store from the list
5.Tap Force Stop (doing this will automatically stop google playstore from running)
6.Tap Clear Cache
7.Tap Clear Data. You can repeat this process for “Download Manager”.

After doing this, your Google playstore should work perfectly and flawlessly again. You can apply this trick to any of your application that is misbehaving and it should solve the problem but if it still refuses, install the upgrade or latest version of that application.
Source: http://www.wizytechs.com/2015/09/how-to-fix-google-playstore-download.html?m=1

Here.. http://www.techrez.com/how-to-fix-android-download-error-198/