I have the server installed, I installed Wordpress as well. When I try to do ulpoad from some file by Wordpress informs me that I do not have write permissions. However all folders are with 755 permissions And when dealing with a reseller to a customer, will not be a big problem?
The files need to have the permissions of the web. You should upload them using a web ftp user or chroot user or chmod them afterwards.
and ensure that you use php mode php-fpm or php-fcgi in that website and that the suexec checkbox is enabled in that site.