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.
There are a lot of definitions of SEO (spelled Search engine optimisation in the UK, Australia and New Zealand, or search engine optimization in the United States and Canada) but organic SEO in 2019 is still mostly about getting free traffic from Google, the most popular search engine in the world (and almost the only game in town in the UK in 2019):

Anchor Text is the visible text on a link or button that you can click on. Google uses this text to determine what the linked page is about. For example, if you set "Learn More About Bike Repairs" as the Anchor Text for the link that goes to your repairs page, it tells Google that the linked page is most likely about bike repairs. When building your site with our site builder, make your Anchor Text as descriptive as possible and avoid using generic Anchor Text like "Click Here" as this doesn't help Google categorize your pages whatsoever.
In December 2009, Google announced it would be using the web search history of all its users in order to populate search results.[33] On June 8, 2010 a new web indexing system called Google Caffeine was announced. Designed to allow users to find news results, forum posts and other content much sooner after publishing than before, Google caffeine was a change to the way Google updated its index in order to make things show up quicker on Google than before. According to Carrie Grimes, the software engineer who announced Caffeine for Google, "Caffeine provides 50 percent fresher results for web searches than our last index..."[34] Google Instant, real-time-search, was introduced in late 2010 in an attempt to make search results more timely and relevant. Historically site administrators have spent months or even years optimizing a website to increase search rankings. With the growth in popularity of social media sites and blogs the leading engines made changes to their algorithms to allow fresh content to rank quickly within the search results.[35]
Goals and Objectives. Clearly define your objectives in advance so you can truly measure your ROI from any programs you implement. Start simple, but don’t skip this step. Example: You may decide to increase website traffic from a current baseline of 100 visitors a day to 200 visitors over the next 30 days. Or you may want to improve your current conversion rate of one percent to two in a specified period. You may begin with top-level, aggregate numbers, but you must drill down into specific pages that can improve products, services, and business sales.