Hi,
You have two options:
1. you edit the file show_block_terms via the menu Display>Views and change the line:
JRoute::_('index.php?option=com_hikashop&ctrl=checkout&task=termsandconditions&step='.$this->step.'&pos='.$this->module_position.'&tmpl=component'),
to:
'https://mywebsite***.de/index.php?option=com_it-recht-kanzlei&type=agb&tmpl=component'),
2. You install that extension
extensions.joomla.org/extension/components-anywhere/
in order to have in a joomla article the tag corresponding to your com_it-recht-kanzlei component and then select that article in the Terms & Conditions view of your checkout workflow.
The advantages of the first solution are that it's more lightweight, you don't have to add an extra extension just for that, and should not need any update for the foreseeable future.
The advantages of the second solution are that this will work far into the future, even if we change the checkout code a lot, without you having to change your view override and you can have several terms and conditions views in your checkout linked to different joomla articles (the first solution will always display the link you entered in hard in the view override code).