You can easily post screen shots or camera photo (reduced in size) by using the paperclip icon in the edit panel of your message. Also you can use gdisk to list partitions. I suggest adding gdisk as it is a tool to see & edit gpt partitions.
Not sure if it is true with gpt drives, but with MBR we always suggest to use the Windows tools to shrink the Windows NTFS partition, then reboot several times, so it can run chkdsk and recognize its new size. Also backups of the Entire Windows & a Windows repairCD should be made just in case. Also backup efi partition, there was a bug in earlier versions of the installer/grub that overwrote the efi. It is fixed in current version, but if you happen to try an older install it still will have that bug.
Ubuntu will run in as little as 5GB, but that requires significant effort to regularly houseclean. It depends a lot on what you plan to do and if not sure the default install of just / (root) and swap in the 50GB unallocated is fine. Alternates are two added partitions, a separate partition for /home and separate NTFS partition for shared data.
I usually suggest separating systems (both Windows & Linux) from data. Since /home is mostly data many of us suggest separate /home partition.
And Windows does not like a lot of writes into its system partition. LInux' NTFS driver exposes all the normally hidden files & folders so it is easier to accidentally move or delete something. I used to unhide everything in Windows and regularly did something that required major repairs. So I might make the Windows system partition smaller and create a shared NTFS data partition. That was the first thing I did with my system and it allowed me to move the Firefox & Thunderbird profiles to my shared. Then I did not have to reboot to see email or have all my bookmarks from Windows.
You can use gparted to create the Linux partitions as it works with gpt partitioning, if you want to create partitions in advance. One advantage of gpt is all partitions are primary. I do not notice any difference in using gparted with gpt drives or MBR other than there is no logical drives.
GParted partitioning software - Full tutorial
My standard suggestion, others may have different opinions and many of us use system differently so needs vary. I find my own optimal partitioning is not so good a couple of years later, but then buy a new drive anyway.
For the Total space you want for Ubuntu, You already have the efi partition, an do not need the bios_grub if only booting UEFI:
Ubuntu's standard install is just / (root) & swap, but it is better to add another partition for /home:
If gpt(not MBR) partitioning include these two first - all partitions with gpt are primary
250 MB efi FAT32
1 MB bios_grub no format
Ubuntu partitions - smaller root only where hard drive space is limited
1. 10-25 GB Mountpoint / primary or logical beginning ext4(or ext3)
2. all but 2 GB Mountpoint /home logical beginning ext4(or ext3)
3. 2 GB Mountpoint swap logical
Depending on how much memory you have you may not absolutely need swap but having some is still recommended. I do not hibernate (boots fast enough for me) but if hibernating then you need swap equal to RAM in GiB not GB. And if dual booting with windows a shared NTFS partition is also recommended. But you usually cannot create that as part of the install, just leave some space. Or partition in advance (recommended).
One advantage of partitioning in advance is that the installer will use the swap space to speed up the install. Thanks Herman for the tip.