On-page SEO, a.k.a. on-page optimisation, is a combination of your heading tags, meta information, content, site structure, outbound links, page speed, and other signals that affect your search engine ranking and visibility. 

Google & other search engines continuously update their algorithms for the latest digital trends and to provide the best web pages to users. You can’t control their algorithms, but you can control the information you send to Google through your on-page seo. If you have an optimized website, you’re sending the clear signals to Google (& other search engines) about what your website is about and have a better chance to rank where you want to.

Nobody can guarantee website ranking in any search engine.  Because ranking depends on so many factors like keyword research, niche research, and backlinks.  On-Page is one of the factors amongst them. On Page SEO  will increase the chances of your website for organic search presence. 

Ranking Depends on different many factors. It is a constant, sincere & continuous effort. No page get rank in SERP just overnight. Normally it takes months to see the results. During this period, all you need is constant optimisation of your pages & continue to update the site. You will surely see the results.