Thank you so much for using our theme Quality Constructions.
1. If you want to make your website multilanguage, you can use polyglots plugin. https://wordpress.org/plugins/polyglots/
2. In case of slider, you can use plugin. We suggest you to use this one. https://wordpress.org/plugins/master-slider/
Please try with this plugin to make the site awesome.
You can check the video to know more about the theme functionality. https://www.youtube.com/watch?v=3NcOR_RRn5Y&t=160s
With Warm Regards