SQL Server 2016 login language display is wrong
If the change (Alter login LoginName  with DEFAULT_LANGUAGE  = English) applied successfully (Commands completed successfully.) the language must be changed though server default is Arabic. 

However, you have to disconnect the session and connect with new session then try select @@language. 

If you have already done so, and the problem still persist, check SQL Error log if there is any issue reported while changing language for particular login.