OEM 40MB partition filling up

Fyi, image uploads to this forum are only visible to the person who posted them and to Dell reps, so I can't see what you're seeing.  But if you recently upgraded to Windows 10 1803, it seems that in some cases the Recovery and/or OEM partitions that are normally supposed to be hidden are getting assigned drive letters and triggering low space warnings.  Those partitions aren't really filling up; they've always been close to the maximum because they don't normally grow, but Windows was ignoring them while they didn't have a drive letter assigned.  You can remove the drive letter by following the steps in this article.

As for deleting, yes you can delete that OEM partition, but it's not in a space that would allow you to repurpose that storage anywhere else in a useful way, even if 40 MB was a worthwhile amount of storage to repurpose in the first place, so I wouldn't bother.  But if you ever did a clean install or an image restore, you could certainly delete/omit that partition.  As for the Windows Recovery partition, that's a separate entity.  Even if you never use it, Windows will recreate it during every Windows 10 release upgrade if it doesn't exist, and in some cases it's required if you use BitLocker, so I would just leave it there even if you never intend to use it.