Setting up multisite

We have a website called icelandictimes.com and yesterday I was trying to put up multisite on it. I first tried it on another site and it worked fine but when I did it on the icelandictimes.com website it does not work.

I followed the instructions on this site: https://premium.wpmudev.org/blog/ultimate-guide-multisite/

After I have disabled all the plugins and changed the wp-config.php and .htaccess I try to log in again to the dashboard but am unable to do so. I have attached the photos to show what comes up when I try to do so.

I hope you can help me so that we can start using your plugins. Thanks