Issues with Responsiveness and loading speed

I’m having issues with responsiveness on my site and getting customizations to work (if they’re possible with this theme). Here is my website: http://www.thepowerfulmind.com

When viewing my site on mobile, the logo/title is cut off at the top.

Also, my website takes a very long time to load, is there anything I can do to speed it up? There are no videos hosted on the site, and would like it if it could load faster.

The text display on mobile is also very narrow and looks weird, how can I make it display for the full width of the browser on mobile?

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In addition, I want to change the home page to display only the most recent post, rather than all of the posts that fit on the page, how can I do that? Is there any way to customize the width and position of the footer widgets?