Can't get it to work :/

Hi For me this seems a bit broken, I followed those steps to set up userChrome.css: https://www.reddit.com/r/firefox/wiki/userchrome/

%appdata%\Mozilla\Firefox\Profiles\t8uf0qaw.default-release\chrome grafik

userChrome.css content:

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");

@import url(components/windows_controls_placeholder.css);
@import url(components/hide_tabs_toolbar.css);
@import url(components/autohide_sidebar.css);
@import url(components/enhance_context_menu.css);

/* Remove unneeded context menu entries */
#tabContextMenu #context_sendTabToDevice,
.share-tab-url-item,
#context-sendimage,
#context-sendvideo,
#context-sendlinktodevice,
#context-sep-setbackground,
#context-setDesktopBackground {
    display: none
}

/* Remove sidebar header */
#sidebar-header {
    display: none
}

I've installed sideberry, imported the json data and added the sideberry css into sidebar.

Problems:

The sidebar does not go back at all:
The Tab bar at the top is never hidden unlike shown in the video.

What am I doing wrong?

dexeonify / firefox-css

Can't get it to work :/ #2