Might be less confusing if you take a look at what you have with lsblk first. That might give you a better view of your existing disk layout so you know what you need to do. To your specific question though, I’m pretty sure resizing the LUKS volume is done with some sub-command in crypysetup. I’m not at a proper computer to check, but it’s definitely in the man page.

All that assumes you have LUKS underneath LVM, which is fairly standard practice.

Hope that helps get you pointed in the right direction.