Problem with css editor

Hello.

I have this problem: in my css editor I put a background from

but when I am making tests and clic in save, in the part of colors I see this: “\\\\\\\\\\\\\\” and more and more they increase.

Here You can see teh problem: http://prnt.sc/b79w23

And sometimes I get An error when make clic in save CSS.
Error: error line in 1811 line..

https://wordpress.org/plugins/contact-form-7-style/