Drupal patch files - Why do Drupal patches have complicated file names?
It just provide good information about the patch.

Here is the proper way to name a patch

[project_name]-[short-description]-[issue-number]-[comment-number].patch


Why? Here is a list of why these name are useful...


[project_name] - We use the project name to distinct the patch from other projects. Sometimes some project have multiples sub-modules and it just nice to have a name in front of the patch.
[short-description] - This is just a well practice from git, which is adding a small description about the patch.
[issue-number] - With unique issue number we can make sure what this patch is trying to solve because we can visit drupal.org/node/[issue-number] and see what is trying to solve. 
[comment-number] Usually, there are multiple patch in the same issue queue and we need way to distinct different patch for this reason we add the comment-number so we do not get confuse when we are reviewing patches.


For more information about patches naming visit - Making a Drupal patch with Git


  And also a subtle question: If I download a file with a long name and
  than changed the name to something like "fix1.patch" just for
  navigation comfortability, Will it still work as normal as it should
  have been?


Patches names does not have any affect to the patch content. This been said, it will work, it just that developer was very lazy and did not want to name it the proper way (or he/she did not know how to in Drupal we name patches).