Finally, found a complete answer.
What I've done to fix the problem-
1. Reinstalled Xposed with newer version and awaited for better network connection.
2. After a day, the problem vanished!
What you should try if the problem persists-
note: These fixes also work for other play store problems.
1. Stop it, wipe it and clear it- You can try going to settings>application>all>Play store and wipe it's data, cache after force stopping it. Also, try doing this for Google play services if problem persists.
2. Switch to a better connection- A lot of apps won't install of your internet connection is sluggy. Try switching to Wi-Fi else.
3. Uninstall and reinstall the app- For those with root access, you can try uninstalling Play store and reinstalling it from another source. (See last of the answer to find some websites.)
4. Refreshing your Google account- The problem may occur due to some error in your account. Try removing your Google account and adding it again.
Other Google Play Store errors and fixes
Error 498: Phone's cache is full. Try wiping it.
Error 919: Phone's storage full. Try uninstalling apps.
Error 403: You're using two different accounts on your device.
Error 927: The play store is updating. Try again later.
Error 101: Too many apps installed. Remove a few.
Error 919 (second): Your APN settings aren't correct.
An xda thread which will guide you through various error codes-
Also, if using any VPN app or adblocker, try removing them.
Why modifying android causes malfunction in Play Store?
While rooting or doing other things related to it, you are (directly or indirectly) modifying system files. Some alternations to system directory can cause play store to stop functioning. A major cause is flashing custom ROMs.
There is an app for that
A great app by QuillApps, known as Android error code fixer can solve your problem. Try it and let everything on it.
If everything else fails
And, in case everything else fails, try other apps like mobogenie, f-droid, amazon and many more. They also contains apps that are unavailable on Play store.
Some trusted websites for Play Store apk:- Androidpit.com, androidapksfree.com, apkmirror.com and much more. Try googling it.
Please do not down vote for anything above offtopic. As I'm new to this, I don't know what's offtopic. :p
Please appreciate the answer if helped. Before editing, please ask me.