Multiple Disk Partitions in HDD

One note in addition to the above: If the repartitioning I described sounds a bit daunting, there are partition manager applications available.  I've heard good things about EaseUS Partition Master, and it has a free version that would do what you need, but I've admittedly never used it myself.  Still, it might be worth looking into, although again I'd still strongly recommend making an image of your system before messing around.

The image partition is an image of your system as it shipped from the factory that can be used to reset the system to its "out of the box" state.  If you don't think you'll ever want to do that because you'd be comfortable performing a clean install of regular Windows 10 from Microsoft, then you can delete it.  I'm not sure what the Dell Support partition is because the onboard diagnostics are embedded into the firmware.  I've read that it might contain tools that allow Dell to remotely access and control your PC even if Windows isn't working, but I've never confirmed that myself because I always wipe my hard drives and start with a basic Windows install when I get new laptops anyway, so my systems don't have those partitions.  However, there are other partitions you definitely need to KEEP.  They will typically be the ones on the disk before your C partition, and there might be a Windows Recovery partition either at the beginning of the disk or immediately after your C partition, depending on your Windows 10 upgrade history (more on this below).  So first of all, be careful deleting things, in fact you might want to capture an image of your system in its current state before you start messing around with deleting partitions.  Macrium Reflect Free is a popular tool for this purpose.

But if you want to start deleting partitions, you might be able to do it just from Disk Management.  If the delete option there is grayed out, then you can use the diskpart command-line tool.  To use that, open Command Prompt and enter the following:

diskpart
list disk
select disk X (replace X with the number of your disk, based on the output of list disk)
list partition
select partition X (replace X with the number of a partition you want to delete)
delete partition override
(Repeat the last two commands with different partition numbers to delete additional partitions)
exit

Then if you close and reopen Disk Management, you should be able to shrink your C partition as desired and then create a new partition in the unallocated space.  The only potential issue will be if your Windows Recovery partition is currently after your C partition.  If so, ideally any additional partitions you create would exist after the Recovery partition, but that would of course mean that you couldn't shrink your C partition to create capacity for a Data partition, because then the Data partition would be between the C partition and the Recovery partition.  In that situation, the proper solution would actually be able to capture an image of the Recovery partition, delete it, shrink your C partition, restore the Recovery partition into that free space directly after the C partition, and then create the additional Data partition after that restored Recovery partition.  The basic reason for this is that when you upgrade to newer releases of Windows 10, if the new release requires a larger Recovery partition than you currently have, Windows will shrink your C partition to create the necessary additional capacity.  If the Recovery partition exists immediately after C, it simply shrinks by the additional amount necessary and resizes the Recovery partition to use that space.  But if you have some OTHER partition after C (e.g. C partition, Data partition, Windows recovery partition), Windows will shrink your C partition by the ENTIRE amount necessary to create a completely NEW Recovery partition and leave the old one around as dead weight -- so you'll end up with C partition, new Recovery partition, Data partition, old unused Recovery partition.  At that point technically you could of course delete the old Recovery partition, but as you can see, it's a bit messier overall.