Question about SEO for specific theme

Hi guys. I have build a website on top of this WordPress theme https://sequentialdemo.wordpress.com/ , here is adress of my website – https://astrazlata.rs . This theme have some little bit unusual design (I didnt think about it when I started to build site). On my front page of website it looks like the entire page is build from one page, but its opposite, front page is build from three pages pocetna, https://astrazlata.rs/knjigovodstvene-usluge/, https://astrazlata.rs/promo/ . Now I want to do SEO for this website, but it gives me a headache, because I wanted to do SEO for specific keywords for entire front page, but I can’t because front page consist of three different pages. Is there any solution for SEO for this website design, or I should change a theme?