MediaWiki:Common.css

/* CSS placed here will be applied to all skins */
.mw-logo-icon {
    width: 85px !important;  /* Adjust size */
    height: 85px !important;
}
.citizen-header__logo {
    display: none !important;
}
/* Hide top statistics counters (Pages, Files, Users, Admins) */
.citizen-drawer__stats {
    display: none !important;
}

/* Hide Help about MediaWiki in the navigation drawer */
.citizen-drawer #n-help,
.citizen-drawer a[href*="Help:Contents"] {
    display: none !important;
}

/* Hide Special Pages in the navigation drawer */
.citizen-drawer #t-specialpages {
    display: none !important;
}