Solution:

/opt/lampp/phpmyadmin/config.inc.php



$cfg['Servers'][$i]['auth_type'] = 'config';
$cfg['Servers'][$i]['user'] = 'root';
$cfg['Servers'][$i]['password'] = '';
/* Server parameters */
uncomment and change  
//$cfg['Servers'][$i]['host'] = 'localhost';  to  $cfg['Servers'][$i]['host'] = '127.0.0.1';

$cfg['Servers'][$i]['host'] = '127.0.0.1';

$cfg['Servers'][$i]['compress'] = false;
$cfg['Servers'][$i]['AllowNoPassword'] = true;