How to edit the Home page? How to add content to Blog?

My seo/developer had created this website for me and I am trying to edit the landing page for poolcleanup. Initially in the pages there was a page named Home and had no content on it and yet the main page had the content. Therefore I copied the content on the Homepage since I am unable to edit the existing landing page and pasted it on the Home in the Pages section.

I can edit the Home in Pages but I couldn’t make that as the main landing page of the website. I tried to change the Frontpage displays to static from the Front page Home to Posts page Home but when refreshed a blank page shows up. When I choose the Front page Home it is not the same Home page in the Pages that I created. It goes back to the page my developer had created and I cannot find that page to edit. What am I doing wrong? Please advise!

Secondly, I want to enter content to my Blog and I went to posts > categories and the Blog appeared on the right top corner. Therefore I created a new post but it did not appear in the Blog. Obviously it wasn’t supposed to be like that. Please view my site and click on Blog and see what do I need to do to enter content there.

Thanks in advance!