I would advise activating Memcache through these changes in your Magento root folder > app > etc > env.php.
From: 'session' => array ( 'save' => 'db', )
In: 'session' => array ('save' => 'memcached', 'save_path' => '127.0.0.1:11211'),
Then remove these files: rm -rf var/cache/* var/page_cache/* var/session/*
This will improve your website speed.