URL (not slug) shortening and trailing slashes in Yoast

I am using Yoast SEO Premium, and my site is under construction. My question relates to Pages. (I think this is also about Permalinks, but I am not sure.) I did search the support forums for some time before posting my question.

Since it is a good idea from an SEO perspective to stick to only one version of a URL, I have decided to have no trailing slashes at the end of my URLs. QUESTION 1: How do I stop them from being created in the first place? The Yoast snippet preview shows a trailing slash.

The Yoast Snippet preview also shows a shortened version of the URL. For example, if the ‘real’ URL is
https://example.com/books/dictionaries/english-afrikaans
then the Yoast Snippet version is rendered as:
https://example.com/english-afrikaans/

QUESTION 2: Is it ‘bad’ to have a deep URL hierarchy? Should my slugs rather be more descriptive? E.g. in this case, something like
english-afrikaans-dictionary
so that it will be rendered as
https://example.com/english-afrikaans-dictionary

QUESTION 3: Did I create this situation myself? If so, where do I change it (if it is a good idea to change it?) I know where to change the code for post titles such as categories, tags, pages and posts. I don’t know where to change the URL settings.