Is there anything malicious with play support libraries? I was doing my daily stuff on my Android Nougat.

And then something started downloading, play support libraries. I think OK right. But the moment downloading stopped, and installation started my mobile's screen started showing black screen for 2 secs with of a interval of about 5 secs. It continued for about 2 mins. And then the black screen was no longer appearing. But, now my phone started lagging.

So, I was thinking if that was indeed play support libraries or something else.

I'd also noticed that the first character of any word was not capital, i.e. play support libraries.  Which is a small mistake lazy developers often make while making vulnerable apps with the name of any system app, e.g. phone / settings, so the user doesn't notice, after the app gets installed silently, and can do it's work without interference.

So, Is there anything I can do to check if my mobile's safe or not?
What are the Android Support Libraries?


  The Android Support Library is a set of code libraries — resources that can be used to build features and/or functions into an app — that provide things like features or widgets that would normally require an actual Android framework API to include in an app.


The article goes on to state that:


  There are generally two types of support library packages. One set enables features of new versions of Android on devices running an older version and the other provides standalone features for all versions of Android. Because these aren't part of Android proper, they can be improved and updated without waiting for a major Android platform release.


Why are the Android Support Libraries important?


  we don't have to wait for the next version of Android to get an update if a feature is provided by the Support Libraries. This allows developers to add and improve how their apps work, especially on phones that don't run the current version of Android, whenever the libraries are updated.


Your device is not infected by a virus or something else. It is just Google deciding to update your device (even when did not want the update to add more features).

That said, on this thread from Google, there are other users who have noticed lagging the first few minutes after the update.

Source: What are the Android Support Libraries and why are they important?