Performance problems (Urgent)

Hi,
I have install the Newspaper template , But it made my site very slow , i have activate the defaults template of wordpress it very fast , i have implemente all instructions in your documentation but no result

for info : I am using WP fatest cache , because WP Super Cache does not work for me
that is the errors :

Warning! /var/www/alnas/wp-content/advanced-cache.php does not exist or cannot be updated.
1- If it already exists, please delete the file first.
2- Allow / var / www / alnas / wp-content to be writable using the CHMOD command from your FTP client or from your server. (CHMOD 777 / var / www / alnas / wp-content) and refresh this page. This is only a temporary measure, and you will need to switch it back to read-only next. (Go from 777 to 755 in the above command)
3- Refresh this page to update /var/www/alnas/wp-content/advanced-cache.php
If that doesn’t work, make sure that the file /var/www/alnas/wp-content/advanced-cache.php does not exist:

AND

Warning! Unable to upload /var/www/alnas/wp-config.php! WPCACHEHOME must be configured in the configuration file.

AND

Error: Configuration file /var/www/alnas/wp-content/wp-cache-config.php is missing. Please reload the page.