Problem with polish

Hello,
I have a problem with the font.
Plugin does not display Polish characters in the responses.
Maybe encoding is bad, but unfortunately I do not know how to change them.
Please help.

http://www5.cador.pl/wp-content/uploads/2015/11/problem.jpg

https://wordpress.org/plugins/wp-support-ticket/