Drupal 7: An AJAX HTTP error occurred ... Drupal already installed

Hello, I tried to install 6 times Drupal 7 on a Virtual Box machine based on Ubuntu (tried with version 17.04 and 14.04) with different procedure for each one but always I get the same error in the install profile section of Drupal 7

An AJAX HTTP error occurred. HTTP Result Code: 200 Debugging information follows. Path: http://home4.com/install.php?profile=standard&locale=en&id=1&op=do StatusText: OK ResponseText: Drupal already installed | Drupal @import url("http://home4.com/modules/system/system.base.css?0"); @import url("http://home4.com/modules/system/system.admin.css?0"); @import url("http://home4.com/modules/system/system.menus.css?0"); @import url("http://home4.com/modules/system/system.messages.css?0"); @import url("http://home4.com/modules/system/system.theme.css?0"); @import url("http://home4.com/modules/system/system.maintenance.css?0"); @import url("http://home4.com/themes/seven/reset.css?0"); @import url("http://home4.com/themes/seven/style.css?0"); Drupal already installed To start over, you must empty your existing database.To install to a different database, edit the appropriate settings.php file in the sites folder.To upgrade an existing installation, proceed to the update script.View your existing site.

I can't understand why, I tried different procedure, edit permissions, delete, rebuild databases on MySQL and the webserver folders but nothing, modified php settings (based on drupal documentation). he write 31 tables on MySQL and it stops. Any ideas?

The last procedure I followed is https://www.digitalocean.com/community/tutorials/how-to-install-drupal-o...

Thanks for the help.