All countries are capitalized in Greek (Ελλάδα, Γαλλία, etc).
As for the languages, it's a mess. On the website of Babiniotis, a very famous Greek linguist and former professor of the university of Athens, I have read that languages must be capitalized. However, in the European manual for Greek texts, I've read that languages in modern Greek must not be capitalized.
I never capitalize languages, but most people that I know capitalize them. So it's your choice, to capitalize them or not. :-)
See my reply to your comment here https://forum.duolingo.com/comment/17523517$comment_id%3D29917028 ^.^
any ik- ending is stressed at the very end. politikOs, politikE, anglikOs, anglikE. The -ik- suffix means “pertaining to” whatever it is attached to: politikos = someone pertaining to the polis, glossa anglike = a language pertaining to Angles = English, anglika = (things) pertaining to Angles = English as well.