An unexpected error occurred

You do not have any plugins installed yet, correct?
Try switching your current theme to the default 2016 theme if you are not using it already. Try to install a plugin.

I have installed a new premium theme. Should I change to the default theme? But then how to use my premium theme?

This is just temporary in order to test to see if your current theme is interfering with WordPress.

If after that also same problem persists then what to do?

Being as you have only the one extra theme and no plugins, a reinstall of the WordPress core files would be next. This is done with no loss of content.

I reinstalled wordpress but problem is still there… I am not able to install plugins and showing “An unexpected error occurred. Something may be wrong with www.remarpro.com or this server’s configuration. If you continue to have problems, please try the support forums.”

I reinstalled wordpress but problem is still there

What files/folders did you replace?

And can you login to your site?

yes, I can log in my site, but can not access plugin section…whenever I try to do that I am getting this error.
I have not changed any files/ folders.I have just uninstalled everything with taking back ups and then again reinstalled everything

I have not changed any files/ folders.I have just uninstalled everything with taking back ups and then again reinstalled everything

So, you made backups and then reinstalled from the same backups – or former backups?

same back ups

Try this solution.