Many e-commerce webmasters hold the view that when they list a lot of items, everything will translate to higher traffic, better SEO ranking, and sales. However, this is never the case. This can have a devastating effect on bounce rate. A lot of SEOs will tell you to fix the foundation of your website, meaning the template. I think content is the foundation of the website and your template(s) should serve that content. Google Search Console Help Center has a set of instructions that you can follow on how to build and submit a sitemap. If you have a WordPress site, though, you can sit back and relax as a sitemap is already automatically generated and submitted to search engines for you.