It works!

Congratulation, you have just installed your custom web app.

Edit this site

First way to edit this site is by putting your files in /var/www/my_webapp__2/www using SSH/SCP.

Alternatively you can achieve the same thing using SFTP. To do so, you can use a client application such as FileZilla. Here are the SFTP connection details:

Domain
flo210500.de
Port
22 (or the port you defined if you changed the SSH port)
User
my_webapp__2
Password
the one you set at installation

As a reward, here is a random cat picture: