Help with installing on an ext HDD

[admin]

When you use WinToUSB to create Windows To Go, you can select the  "Keep the existing partition scheme" option to use the existing disk partition layout. However, the partition layout must meet certain conditions, for more infomation please refer to the link below:
https://www.easyuefi.com/wintousb/resour...to-go.html

Thank you for the reply.
yes i read that all, and awkward to ask it here again, but please clarify followings as you should be expert in these things.

can i use the shrink feature in the disk management to create the required system and boot partitions? will it allow the rest of the stuff in my external drive to be?
i don't even want to try that because i have very very important data in that. 
i have about 200 GB free space, all i ask is, 
can i shrink that and will be able to create those required partitions using the freed up space? will the rest of the stuff stay as it is during all these stuff i don't want to mess up the drive. 
also previously i tried installing win7 to a usb flash drive which worked  flawlessly but the windows kept giving me pagefile error . this is understandable as windows 7 can't create page file in usb storage. any way to circumvent this? does windows 10 has this issue too? or an internal HDD is a must for this?

thanks in advance.   

Yes, of course you can shrink the existing partition to free up space and then create the system and boot partitions. Windows 10 does not have paging file issues, therefore, we recommend that you create Windows To Go using Windows 10 and an external hard disk. Also, if you're still worried about your data, buy another external disk to create Windows To Go.