Refactor content

• Typos issues by Christian

• Hide not finished chapters

• Introduction

• Chapter 1

• Chapter 2

• Chapter 3

• Chapter 4

• About Us

• Task 1

  1. Select the Conference type
  2. Enter the Title: "Getting started with Git"
  3. Enter a Start/End Date: one month from now

Based on the the course feedback the following remarks are made:

• An introduction round for the later group work should be incorporated.
• People preferd the std. videoconf settings over the gather approach.
• An improved differentiation between lecture and hands-on/tutorial content.