SEO requires a lot of work, a lot of time and a lot of patience. It is a long term process that builds long term value. It takes time to execute a strategy, research keywords, create content and build links and authority and resolve technical issues.
It's a never ending process there is always work to be done.
It also takes search engines time to discover and reward your site for the improvements made and it being reflected in the search results.
It is also important to understand that search engines are continually changing to improve their results and deliver what people want and that we hve no control over this. Sometimes these changes are algorithmic and other times it is the presentation.
You are optimising for two audiences: search engines and real human beings. The search engines know that and you will be rewarded by making the content valuable to human beings so that it can provide search results which are useful and helpful.