My idea is to create a kind of growing form. Now the question is: What is the best way to do this? I haven't found a library, yet. On the picture below, you can see how I thought it to be. It should go to the next step after each input and an EditText field should appear. Any advice on existing libraries or tips on which UI component should be used to realized would be appreciated. Thanks for the help!

you have plenty approach but the one i prefer to use:
make your list, then for each index assign its next EditText. by default make your all EditTexts (except first one) disabled. then add a listener each index to observe its text. as soon as it was filled tell that listener to enable its next EditText.
maybe its not so efficient but its simple and makes code more readable. and also you can extend that easily if you just implement two first indexes because the rest is just the same.