Learn the steps of Internet analysis, if you want to learn Internet marketing for free. For anyone who knows the basics of social media, search engine optimization (SEO), Google news and website building blocks, then you can likely learn Internet marketing on your own. A big part of marketing is understanding your competitors, data and market analysis.
A navigational page is a simple page on your site that displays the structure of your website, and usually consists of a hierarchical listing of the pages on your site. Visitors may visit this page if they are having problems finding pages on your site. While search engines will also visit this page, getting good crawl coverage of the pages on your site, it's mainly aimed at human visitors.
Robots.txt is not an appropriate or effective way of blocking sensitive or confidential material. It only instructs well-behaved crawlers that the pages are not for them, but it does not prevent your server from delivering those pages to a browser that requests them. One reason is that search engines could still reference the URLs you block (showing just the URL, no title or snippet) if there happen to be links to those URLs somewhere on the Internet (like referrer logs). Also, non-compliant or rogue search engines that don't acknowledge the Robots Exclusion Standard could disobey the instructions of your robots.txt. Finally, a curious user could examine the directories or subdirectories in your robots.txt file and guess the URL of the content that you don't want seen.

TASK – If running a blog, first, clean it up. To avoid creating pages that might be considered thin content in 6 months, consider planning a wider content strategy. If you publish 30 ‘thinner’ pages about various aspects of a topic, you can then fold all this together in a single topic page centred page helping a user to understand something related to what you sell.

Ask for a technical and search audit for your site to learn what they think needs to be done, why, and what the expected outcome should be. You'll probably have to pay for this. You will probably have to give them read-only access to your site on Search Console. (At this stage, don't grant them write access.) Your prospective SEO should be able to give you realistic estimates of improvement, and an estimate of the work involved. If they guarantee you that their changes will give you first place in search results, find someone else.