Recently I was trying to free the system disk and moving the user directories to a portable disk. But Ubuntu system will automatically re-make a new one in the former path to store files e.g., the screenshots in image folder. Or if you switch the system language, these user dirs name may still follow your former language.
If you have similar problems, here is a solution.
Open it in terminal:
Change your interested locations there:
# This file is written by xdg-user-dirs-update
# If you want to change or add directories, just edit the line you're
# interested in. All local changes will be retained on the next run.
# Format is XDG_xxx_DIR="$HOME/yyy", where yyy is a shell-escaped
# homedir-relative path, or XDG_xxx_DIR="/yyy", where /yyy is an
# absolute path. No other format is supported.