How to change "Comment" settings

Hi I would like to change the settings in the comments. Under every post I publish there is "By Sarah Althaus" and for ex. "6 comments". I would like to change this in german like: "von Sarah Althaus" and "6 Kommentare". As well at the end of the post before you can read the comments it says "6 comments" and I would like it to "6 Kommentare" (-> in German). How can I do this? Thank you for your support. www.rapunzel-will-raus.ch