Cannot edit system configs for HA installed as VM in QNAP

I found /etc and / directory files are not kept edits once I reboot the virtual machine. They all show “overlay” as mounting type.
My config:
HomeAssistant last version
On Virtualization Station in QNAP NAS using .ova from Alternative - Home Assistant

  • Core 2023.11.3
  • Supervisor 2023.11.6
  • Operating System 11.2
  • Frontend 20231030.2

Filesystem Size Used Available Use% Mounted on
overlay 30.8G 5.9G 23.6G 20% /

I want to change default editor from vi to vim in /etc/zsh/zshrc or /.zshrc
I also want to add vimrc to customize vim.

Thank you for any help!

Anyone can help me?