You must ensure that your content has been indexed by Google. Because some blogs, like Medium, have a high DR (Domain Rating), if an article is shared immediately after being published but hasn’t been indexed by Google, it will rank higher than your blog. Sharing on these blogs is like a way to market your blog post, so it’s completely natural.

You can definitely write about tents, but you should make sure that the two articles do not have duplicate search intent. To limit this, you can search for keywords and check the SERP to see if it returns the same result for different keywords. If there is duplication in SERP, you should not write two separate articles. If there is no duplication, congratulations! You can write two separate articles.

I guess your website is a new website. Typically, new websites are indexed and then may lose their index for a while. I’m not sure if this is an error or intentional from Google. You should regularly check and resubmit it in the Google Search Console. Additionally, sharing your articles on social media platforms can also help improve the indexing of your website.