For more information please visit https://www.janolaw.de/agb-service/einbindung-typo3.html
The recommended way to install the extension is by using Composer. In your Composer based TYPO3 project root, just do
composer require typo3-ter/janolawservice
or
composer require janolaw/janolawservice
Download and install the extension with the extension manager module.
If you update from an older Version (0.x oder 1.x) to Version 2 an update of the database structure is needed.