Organizing search in Drupal Commerce. I have site (e-shop) that uses Search API. Just Search API, Search Autocomplete, Display Suite Search and Database Search are enabled. It was not configured by me.

However, we have big problem. Search returns strange results, we cannot use search by brand cause when we choose brand on Exposed Filter with AJAX and catalog reloads, add to cart product's forms wont work cause forms were rebuild and there's no workaround for this issue.

Can you tell best (and modules) way to organize search in Commerce shop?

Do I need to use Facets and Apache Solr - technologies, which are not used now?
You can use the Search_api_db to avoid Apache Solr. Facets come in many flavors, there's no standard tutorial but some googling will get you started...