Removing header with logo and putting name of site in sidebar

I hope I have posted this in the right sub-forum. There isn’t a forum page for the theme I am trying to modify.

I want to create a fairly minimalist site for myself, but my knowledge of web design is very basic and out of date. I have found a theme that does most of what I want (once I have changed a couple of fonts etc.) https://dessign.net/freeminimalisttheme/, but there is one important thing that I can’t work out how to change. This theme has a header with a logo in it. I would like to get rid of the header and the logo altogether and move the title of the page (as text instead of as a logo) into the side bar, above the navigation menu, so that the site looks a bit more like https://www.leabelooussovitch.com/, with the main image for the page being the first thing that a visitor sees, instead of the logo. I have searched through all the php files and all the css files that I could possibly imagine might be involved in setting up the header and deciding what goes in the side bar, but I just can’t work out what it is I need to change. I don’t know whether I am asking too much to hope that someone can give me a complete answer to my question, but if someone could at least give me an idea what it is that I need to be looking out for, or where I need to look, I would be very grateful.