Getting Error on IIS 8.5

Hi, I’ve been using WordPress for 5 months for this site also using a WooCommerce theme. 2 months ago I have provided the https connection using “certify the web”. I have a windows server and it’s using IIS 8.5 and this site running on that.

The problem is that the web page often gives 500 errors. It does this for a short time, for example only for 5 minutes.

When the last error occurred, I opened the log files and encountered the following error;

“PHP Parse error: syntax error, unexpected ‘}’ in C:\My Sites\xxxxx\wp-includes\class-wp.php on line 308”

Then the error turned to;

“C:\Program Files (x86)\PHP\v7.0\php-cgi.exe – The FastCGI process exited unexpectedly”

And after a few minutes the site is back to its former state. I don’t understand PHP much. I’m a .NET developer, but I didn’t see a bug in the line it gave.

I contacted the theme I purchased and They told me;

“Hi there,

This problem is not a bug of our theme. It may be due to WordPess core or may also be caused by your IIS server error.

Please check your installation package, maybe somehow that file has been wrong.
Contact me again if you have any question.”

I can’t analyze the problem, so I need your help.

The page I need help with: [log in to see the link]