Creating timer with javascript

Since you are using Elementor, you can use their HTML widget for this. See: https://elementor.com/help/html-widget/

Alternatively, you can also store custom code snippets in Elementor Pro: https://elementor.com/help/custom-code-pro/

If you have any questions about Elementor, I would recommend their support forum: https://ww.wp.xz.cn/support/plugin/elementor/

Apart from Elementor, you can also insert individual code into the functions.php of a child theme through individual programming. See: https://developer.ww.wp.xz.cn/themes/advanced-topics/child-themes/ – Or via the Code Snippet plugin: https://ww.wp.xz.cn/plugins/code-snippets/

You can also write your own plugin to add code to your project. See: https://developer.ww.wp.xz.cn/plugins/