Danke - denken - dzienkuje - any connection?

The words "thank" and "think" (in German "danken", "denken") are similar in many Germanic languages. Are they related?

Also, is there any connection between "danken" and the similar words in some Slavic languages, such as

dzienkuje (Polish)
djakuju (Ukrainian)
djekuji (Czech)

I'm sorry if this has been discussed before - I searched the archives without finding anything.

Best regards,
Hakan