small improvments for readme

README.md

 # Castellum Docs
 
-Castellum is a privacy-compliant subject database for scientific
-research.
+Repository for Castellum docs in _en_ and _de_. Castellum is a privacy-compliant 
+subject database for scientific research developed at Max Planck institutes 
+within the Max Planck Society (see [links](#links) for more info).
 
 ## Status
 
 The Castellum project is still in development. Therefore, there may occur some 
 outdated and/or obscure statements in the related docs. Yet, we are eager to keep
-docs and code in sync. Please [submit](https://git.mpib-berlin.mpg.de/castellum/documentation/issues) an issue if you encounter serious problems.
+docs and code in sync. 
+
+Please [submit](https://git.mpib-berlin.mpg.de/castellum/documentation/issues) 
+an issue if you miss a topic or encounter serious problems in understanding the docs 
+or using Castellum.
 
 ## Links