"I know German." would be best translated as "Ich kann Deutsch." (Note that this is not a literal translation. The literal translation would be "Ich weiß/kenne Deutsch", but that sentence wouldn't make any sense in German because the verb "to know" is used differently in German.)
I am guessing you want to know how to say sailed in German. To say that you would say "Segelte"
sprichst du deutsch? is the answer
Ich weiß
SRRY, dont know
all i know is dog in German witch is hund
Ich kenne is the translation in German. It is translated from English to German. German is mostly spoken in the European countries.
"what else do you know?" = "was weißt du sonst noch?"
In german we say Richter. I can pronounce it correctly but I don't know how to describe it, sorry :(
Ich weiß wer du bist.
mehr als du weißt is the translation in German. It is translated from English to German. German is mostly spoken in the European countries.
du weißt - you know (a fact) du kennst - you know (a person) du kannst - you know (how to do something)
From where do we know each other = Woher kennen wir uns?