8 hours ago, mykolas said:I see that there are options of 7.4 ; 8.1 ; 8.2 ; 8.3
OK, you need v7.0+ if you're going to use that faceted search module and PHP 7.2 is what PrestaShop recommends for your version of PrestaShop (although 7.4 will *probably* work fine, maybe).
The system requirements, including php versions can be found on this page and while it says that PHP 5.6 is compatible, that's only the core and doesn't include modules.
The original error you got was because the faceted search module uses a new feature "return type declarations" (the : void at the end of line 77). Support for this was added in PHP 7 which is why you get that error - PHP 5.6 doesn't support it. These new language features are documented here.
You can either remove modules which require PHP 7.0+ (such as the faceted search module, but there may be others), downgrade modules to older versions that work with PHP 5.6 or upgrade your PHP to version 7.2 (or maybe 7.4 if 7.2 isn't available on your server).
PHP 8 isn't supported for your version of PrestaShop. I use PHP 8.1 for PrestaShop 8.1.x though, so upgrading may also be something you may want to consider.