change themes.css in magento2

I am new in magento2.

I have done some changes in a css file and have change the file https://agoshop.at/pub/static/frontend/smart_media/smart_media1/de_DE/css/themes.css on the ftp server.
Here my changes:

Code:

.cathead a.level-top {
  background-color: #75dbfa;
  margin-top: 3px !important;
  color: #000 !important;
  font-weight: bold !important;
  font-size: 13px !important;
  text-transform: none !important;
  font-family: "Open Sans" !important;
  line-height: 22px !important;
  padding-top: 8px !important;
  padding-bottom: 14px !important;
}

But when I open my website agoshop.at I the css will not change.
So I hope someone can help me there how I can do the changes in a css file.
kindly regards for any answer.