I have added one extension but now I have removed that extension. After removing that extension I am getting 504 gateway timed out issue http://prntscr.com/kpc242. Please help is it because of server or extension.
The error you are seeing is a result of Cloudflare not being able to access your website.
This can be caused by issues with your server and you may need to contact your hosting provider to confirm if this is the case.