Intro
If you want to do multilingual development on a SAP ABAP Platform system, i.e. you want to have texts like the labels for a data element to be translated to various languages, those languages need to be available in the system. Otherwise neither the translated texts can be stored nor can you access the system (via SAP GUI or via web access) in this languages as you will be redirected to the default language (just as a side note: if you use a Fiori front-end server (FES) to access the system, the languages need to be available in the FES, too; otherwise your request will fallback to the default language of the FES).