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You copy all the files in your wordpress directory and copy them in your locahost folder and export your server database and import the same database in your locahost database.

Now, change your site url to localhost in your database, so that you can use your site in localhost.

You can use mysql command mode for using that.

mysql -u username -p databasename < file.sql

it will help you

Log into your Cpanel and check your error log and tell us what it says.

If you are on a shared host, your hosting guys will set the memory limit you can use. Check with them, what is the max you can use.

Have tried to disable all plugins?
disable plugins

Did you checked your error log about it?

Or maybe give it a try adding this to your htaccess file

php_flag opcache.enable Off

Try deleting your .htaccess file in your wordpress directory through your FTP. And check whether you can access your site or not?

Its hard to help you without any proper info on what exactly the error is about

Try these
Fix Internal Server Error

Seems, your settings for contact form has been reset after the update. Have you checked the settings in your standard contact form plugin?

There are many causes why your site is showing “Intenral Server Error”

Check your error log and tell us what it says

Or else, you just simple change your default port 80 in your config file to some other say port 81 and access your site using https://localhost:81

Simple!

Just change your database settings in wp-config file.

No it was not hacked. Try deleting your .htaccess file and login.

By default wordpress don’t use SMTP to deliver email notifications or system mails. So, mostly if you don’t setup a SMTP server for your wordpress, they are most likely to go to your spam folders.

Even if a new user register at my site also, i don’t get a notification. After researched for a while, i found out that all my wordpress emails were going to SPAM folder. So, i have installed one of the SMTP plugin available at wordpress plugins directory, setup my SMTP address, and now i am able to receive emails correctly.

I hope this helps as this has already happened to me.

Did you checked your WPI error log, it will help us to trace what exactly the problem is. Or else you can switch to Apache by going for Wamp server.

Try Failed Request Tracing in IIS, for tracing what went wrong. It might give an idea.

https://www.iis.net/learn/extensions/url-rewrite-module/using-failed-request-tracing-to-trace-rewrite-rules