Dockerized Nextcloud with Pico CMS and Sub Domain's

Hi folks,
i’m stuck with my own requirements and i have currently no idea how to solve.
Current situation:
I have set up a Linux Debian 10 Host with Docker.
I use Docker Compose to start the following Container:
I reach my Nextcloud installation via this URL:
I have added the App Pico CMS.
My idea was to rewrite or redirect to a Pico CMS Folder inside the Nextcloud installation.

My Issues/Questions are:

  • i do not know where to set the rewrite
  • may be it is better to create a vHost in NGinx?

Has some already done something similar?
Thanx for your help