Thanks for your answer.
I had to reload the website from back up, there was no way to get to any page only through FTP. I tried again and deleted cookies. Didn’t work so from back up again. You can imagine how annoying this is.
I am using wordpress 4.2.4.
Plugins I use:
Akismet
Version 3.1.1 | By Automattic | View details
amr shortcode any widget
Version 2.4 | By anmari | View details
Category pagination fix
Version 3.2.2 | By rahnas | View details
Cherry Parallax Plugin
Version 1.0.0 | By Cherry Team. | Visit plugin site
Cherry Plugin
Version 1.2.7 | By Cherry Team. | View details
Contact Form 7
Version 4.2.2 | By Takayuki Miyoshi | View details
Google Analytics by Yoast
Version 5.4.5 | By Team Yoast | View details
Hello Dolly
Version 1.6 | By Matt Mullenweg | View details
InPost Gallery
Version 2.1.1 | By Rostislav Sofronov | View details
Lingotek Translation
Version 1.1 | By Lingotek and Frédéric Demarle | View details
MotoPress Content Editor
Version 1.5.8 | By MotoPress | View details
Newsletter
Version 3.8.5 | By Stefano Lissa | View details
Polylang
Version 1.7.9 | By Frédéric Demarle | View details
Redirection
Version 2.3.16 | By John Godley | View details
BTW: In the page you shared, or this page: https://help.contactus.com/hc/en-us/articles/200619888-Copy-Pasting-the-Code-vs-Implementing-through-the-WordPress-Plugin it is not explained how to paste the code into html body. What is not so easy when you use a CMS.