Can't finish the scan because of php errors

Hi, I have installed defender to try it on my site and when I tried to perform a scan of my page it proceeded and then it felt down with following warnings:

Warning: set_time_limit() has been disabled for security reasons in /data/web/virtuals/51889/virtual/www/domains/kybernaut.cz/wp-content/plugins/wp-defender/app/module/scan-module/component/class-wd-scan-api.php on line 142

Warning: Invalid argument supplied for foreach() in /data/web/virtuals/51889/virtual/www/domains/kybernaut.cz/wp-content/plugins/wp-defender/app/class-wd-utils.php on line 444

Warning: Invalid argument supplied for foreach() in /data/web/virtuals/51889/virtual/www/domains/kybernaut.cz/wp-content/plugins/wp-defender/app/class-wd-utils.php on line 444

Warning: Invalid argument supplied for foreach() in /data/web/virtuals/51889/virtual/www/domains/kybernaut.cz/wp-content/plugins/wp-defender/app/class-wd-utils.php on line 444

Warning: Invalid argument supplied for foreach() in /data/web/virtuals/51889/virtual/www/domains/kybernaut.cz/wp-content/plugins/wp-defender/app/class-wd-utils.php on line 444

And this message: "Your server resource usage is too close to your limit. Please try again in 15 minutes.".

How I can fix it? Thanks a lot.