Question regarding the layout

Hello! I am new to tutamail, starting my quest to degoogle my life. My problem: I can't find the option to change the layout to a more readable design. Showing the email just in the right third of my screen is too narrow. I have to scroll left and right for every sentence. I'm sure this is not the only option for the layout, but I just don't find the option to change it to a more readable design. Could anybody help me? Or do I have to keep looking for other gmail alternatives? The gmail layout works perfectly for me.