How to retrieve information from GITLAB API

I want to retrieve information from GITLAB repositories like:

• Hours spent on a sprint/Milestone;
• Hours/Time spent on each project;
• Hours/Time spent by each employee

I'm trying to use GitBeaker to do what I need.
Also reading Official Doc

But yet I can't do it.

My code so far:

const { Gitlab, ProjectsBundle, UsersBundle, GroupsBundle } = require('@gitbeaker/node')

const services = new GroupsBundle({
  host: 'http://example.com',
  token: 'XXXXXXXX'
})  

const projects = services.Projects.all().then((project) => {
  console.log(project)
}).catch((error) => {
  console.log(error)
})  

I'm able to retrieve ALL projects, Groups and Users, but what If I want to retrieve only projects from a specific Group?
How may I get the time spent for a specific project?
The lib documentation names a bunch of attributes/properties available, but every time I try something different than Projects/Groups/Users.all() it returns HTTPError: Response code 404 (Not Found).

const projects = services.Projects.Branches.all()  // for ProjectsBundle - 404 Not Found
const projects = services.GroupMilestones.all() // for GroupsBundle - 404 Not Found
etc...