Drone for multi projects in same repository

hello there

I try to get drone working for my multi project repository. I have the following structure:
/.drone.yml
/frontend/ < everything angular… build with npm
/backend/ > everything java… build with gradle

Read the documentation but didn’t find anything about setting the directory for a pipeline.

My current .drone.yml isn’t working:

kind: pipeline
type: docker
name: backend

steps:
- name: build
  image: gradle:jdk11
  commands:
  - gradle assemble
  - gradle check

I get the following error: Task ‘assemble’ not found in root project. Which make sense, because it’s not executing the command in /backend

When /backend works, I will add frontend as new pipeline