Maximum number of links?

When I add a new header, sub-header or sub-sub-header, another is deleted. Is there a maximum number allowed on the Main Menu? I count I have 79 in total.
It’s an attractive theme but I find it frustrating to decide what to include on the front page. I’d like to have an about section but my logo covers the text. I tried putting in a smaller logo for the suggested size of 109×32 and it’s way too small. So I left it large: https://www.partypot.ie
Also, what posts or pages are highlighted in the Latest News section? I can’t see anything in common between all the five posts/pages that are currently highlighted there. I also can’t see the featured image on all of them.
Sort this little things for me and you’ll get 5*