Do not construct long urls to include your "keywords". It is a mistake that will result in a very inflexible site, with all kinds of dupe content problems, and will not help in ranking.
Re URL structure, I suggest looking at this thread... How important is it to organize pages into directories? Sept 2011 https://www.webmasterworld.com/google/4364322.htm
Study the posts by g1smd. Note that there's a bunch of disagreement about whether the url should include the folder hierarchy. g1smd comes down strongly on the side no, the url should not include that hierarchy. You can (and should) still have a hierarchy in your nav structure and in the folders and categories of your site, but the folders should not be part of the url name.
As g1smd puts it...
While the old way was to have a folder heirarchy for the site and show that structure in the URL, nowadays that will often get you into trouble.
The problem comes when a deep content page might be listable in several categories. The deep page will have multiple URLs, with a different path above it. Using breadcrumb navigation simply adds to the problems.
We had a fair amount of discussion about the questions raised by this, and about many confusing side issues, in this forum from roughly 2011 to 2015, and much of that is summarized in the discussion I'll note below, which IMO is one of the best we've had here, not really on site structure, but on url structure. It reviews or mentions many of the issues and discussions I refer to above, and links to many previous discussions that I feel are worth reading if you want a solid overview.
The thread is.... Rewards and Risks of Changing to Hierarchical URL Structure Aug, 2015 https://www.webmasterworld.com/google/4760622.htm
Worth noting again that keywords in the url have at best a miniscule effect on ranking. IMO, where they really help is in what gets highlight in the serp.
Also, FWIW, with regard to this thread, again... I believe it's a bad approach to try to target longtail by creating pages with titles or filenames containing many vocabulary variants.
Also, nav structure is not the same as url structure. That also can get into a long discussion by itself.