Hello deepalijadhav,
One of the more common causes of 500, or internal server errors is the .htaccess file. This file is written to by Joomla for several things. Try and check the Search Engine Friendly URLs article to ensure they are turned on properly. If they are on, turn them off momentarily and see if the site works. If so, turn them back on and it should still continue to work correctly.
If that does not work, you will want to disable the extensions you have set in Joomla and check the site. If it works, re-enable the extensions one by one until you find the one that is interrupting your site. That will be the one that you want to leave disabled or find a replacement for.
Best Regards,
Scott M