This is actually the website with my tumblr posts I could obtain the tumblr posts applying this script,

however i should also import the styling of my actual tumblr too. How do i do that?

Most tumblr theme's get their CSS code found in style tags within the html document (there's different causes of this, but it is standard practise).

Due to this, you will need to make certain that you simply copy All of the css within the theme (included in the HTML file, and elsewhere if relevant) and copy it right into a new css file that you will host yourself.

Download it and upload them there. Then just link it within the template with the addition of before </head> this <link rel="stylesheet" href="path_to_the_place_where_you_uploaded_yout_css.css">