How do I shrink my Ubuntu partition and reabsorb the freed space into my Mac OS Mojave Partition? How do I shrink my Ubuntu partition and reabsorb the freed space into my Mac OS Mojave Partition?

I started with 250 GB SSD, to which I allocated about 65 GB for Ubuntu like 3 years ago. I installed Ubuntu with the help of a friend and online tutorials. I'm not a whiz.

Now I'd like to shrink my Ubuntu partition. I'm willing to remove it if necessary, but it would be cool to keep it around in case I get into that stuff again. 

So ideally I'd shrink it by about 40 GB and then add that space back to my main Mac partition.

I have 4 volumes. 1 is a recovery volume, 1 is the main volume, 1 is the Ubuntu volume, and 1 is something else. (I might have even put Windows on this thing... I honestly am not sure.)

Originally posted on the AskUbuntu site but someone commented it was off-topic there, so posting here in hopes of better results.
For this question, I created a partition called "Ubuntu" but not really Ubuntu. Just a random partition that's only 3 GB but it should work the same way.

First of all, you will have to go to Disk Utility and choose "Show All Devices"



Then click on the top Disk and click "Partition"





You can then click on the "Ubuntu" piece of the pie chart and change the size from 65 GB to 25 GB or whatever you want it to be.



Click "Apply", wait for the process to finish, then it should be resized! Comment if you have any problems.