I know that a SEO specialist can help you conduct a SEO optimization of an online store, but if you are promoting an online store yourself, then this extension https://www.mageworx.com/magento2-extensions/seo-tools-services.html may be useful to you. This is a powerful tool that will help you do the routine work in SEO optimization and will help you in SEO promotion. I think it will be a profitable investment.
content and backlinks. Look up videos by Neil Patel and learn from him little by little. Do not make the mistake that I did and pay some "SEO GURU" 1000 dollars to deliver "guaranteed" results.
Google has the final say and it is difficult to determine what their algorithm likes or does not like. You can follow case studies by Brian Dean as well, I am unable to posts link at this time just do a search for Brian Dean google case study.