Fatal error: Maximum execution time of 120 seconds exceeded in Unknown on line 0

I have a problem while using wordpress with my current website.
This is how you can see it now: https://beyourchange.it/
I was creating a network, to get a subdomain in english for my website, and this problem went through.
Right now I can’t even log into the wordpress dashboard, because the only thing I can see is: Fatal error: Maximum execution time of 120 seconds exceeded in Unknown on line 0.
I have tried adding a special line in the config.php file but it is not working.
I really don’t know what to do!!
There was an issue this morning just after having create the network, I couldn’t see the homepage.
Its was displayed: Index / eng in a blank page.
Can someone help me?