You should work on search engine optimization for your page, focusing more on keyword targeting. If you're not aware of how it works I suggest you taking this 1 hour long course which will provide you the needed information on how to find and target the proper keywords for your page: https://www.bitdegree.org/course/how-to-do-keyword-research
Sign up for the search console (previously known as Google webmasters) and track your website for issues. It will definitely show you the crawling errors due to which your site's urls are not being indexed properly. Cheers!