Hello, @SC,
1. Actually, it is because if you navigate to the dashboard >> Products >> Categories and check there are a total of 15 categories but only three categories have products all others are empty. So once you will add the products to the other categories they will start appearing in the search box categories list automatically.
2. There was a CSS code that caused the issue. Check the code image: https://postimg.cc/ftWfNXWz I have removed it. So that the custom code that I added now in the theme options check here: https://postimg.cc/cgjgb8r5 start working and your issue is resolved. Here is the resulting image: https://postimg.cc/68Xhtfky please check back to your site after clearing the browser cache.
3. Actually you faced this issue because you have not placed the language files in the proper folder, I have moved your language files under wp-content/languages/loco/themes and now you will never lose your files whenever you will update the theme.
I have uploaded the translated files there and you can change any of the words now from the theme language files as per your requirements: https://dev.sioncreativos.com/veqquettal/wp-admin/admin.php?path=languages%2Floco%2Fthemes%2Fxstore-es_ES.po&bundle=xstore&domain=xstore&page=loco-theme&action=file-edit
4. That is actually the custom text and you can change/modify it from Theme options > Header builder > Cart > Mini-Cart Promo Message > Text tab: https://postimg.cc/QF6pgLMq as per your requirements.
Regards 8Themes Team.