Could you recommend me how to develop an enhanced e-commerce for Magento 1.9.x?
I think having an enhanced e-commerce with Google analytics is very good.
There are probably several Extensions out there, which provide this functionality. As you are probably a developer, you can also look up the documentation which values are needed on which page type, apply it normally in Magento.
some more information how to add something can be found here https://developers.google.com/tag-manager/enhanced-ecommerce