Hiding title and underline on pages

Hello everyone,

I tried many ways to hide page titles and underlines, but somehow I couldn’t succeed .

Among others I installed a plugin which supposed to hide titles and I also tried to modify stlye.css, entering the following rows, but none of these options worked.

.entry-header {
display: none;
}

The only thing I can imagine that maybe I don’t put this code to the right place. Now I tried to insert to the very end of the css file.

Do you have any suggestions?

Thank you!