Greasy Fork is available in English.
WhatsApp Web Messages Website Dark Theme Night Mode Simple
// ==UserScript==
// @name WhatsApp Web Messages Website Dark Theme Night Mode
// @namespace english
// @description WhatsApp Web Messages Website Dark Theme Night Mode Simple
// @include http*://*web.whatsapp.com*
// @version 2.4
// @run-at document-end
// @grant GM_addStyle
// ==/UserScript==
// Main - Collapse the Greasy Fork Header
var style = document.createElement('style');
style.type = 'text/css';
style.innerHTML = ' ._11ozL { filter: invert(1)brightness(0.8)contrast(3);} body{filter: invert(1)contrast(0.75)hue-rotate(180deg);}img{filter: invert(1)contrast(1.25)hue-rotate(180deg);} html .NuujD { zoom: 130%;} body .landing-main { background: #000;} ';
document.getElementsByTagName('head')[0].appendChild(style);