Worpdress cannot create directory

add this below line to your wp-config.php (if you did not add it yet)

define('FS_METHOD', 'direct');

Check which user run your servers too (not only php7-fpm).

ps aux|grep nginx

ps aux|grep apache

if your server works on www-data then,

cd ../your_wordpress_dir/
sudo find . -type f -exec chmod 664 {} +
sudo find . -type d -exec chmod 775 {} +
sudo chmod 640 wp-config.php

if you are still getting same error, try a clean installation again with above permissions.