Some unwanted popups & ads are coming when I am trying to download anything from play store. How to prevent this? Can anyone please help me.
I think it is a kind of malware attack i suggest you to install anti malware.
Helpful: Backup your data, account and reset it.
This kind of issue is very common install AdwCleaner.
Once it got installed run for free scan and click on the clear button then finally restart and check.
I hope you are clear explanation with this answer.
Its just okay, you can simply block the ads by doing the following:
Go to Settings > Applications (or Security on 4.0 and above) on your Android device.
Navigate to the Unknown sources option.
If unchecked, tap the checkbox, and then tap OK on the confirmation popup.