My userChrome.css

userChrome.css

@namespace url(http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul);
@-moz-document url("chrome://browser/content/browser.xul"){
    #main-window:not([sizemode=normal]) #TabsToolbar{
        margin-top: 1px !important;
    }

    #:root:not([uidensity="compact"]) back-button{
        border-radius: 0 !important;
    }

    :root:not([uidensity="compact"]) #back-button > .toolbarbutton-icon{
        border-radius: 0 !important;
        border: none !important;
    }
    #main-window[sizemode=normal] #titlebar{
        height: 64px !important;
    }

    .titlebar-placeholder:nth-child(1){
        display: none !important;
    }
}