How to say (i'm familiar with that) in German ?
Hello.
How to say (i'm familiar with that) in German ?

In google translation (ich bin damit vertraut).
but i'm not sure if it's the common way to say it.
-------
How to say (both complete each other)?
is this correct?
beide ergänzen sich einander.

thanks :).

Question

How to say (i'm familiar with that) in German ?
Hello.
How to say (i'm familiar with that) in German ?

In google translation (ich bin damit vertraut). 
but i'm not sure if it's the common way to say it.
-------
How to say (both complete each other)?
is this correct? 
beide ergänzen sich einander.

thanks :).

Answer

1. "Ich bin damit vertraut" is ok, but a bit formal. Some informal ways to say it are: "Ich kenne das", "Ich kann das", etc., depending on the context.

2. "Sie ergänzen sich [gegenseitig]."

3. If you have two completely unrelated questions, I'd prefer that you post them separately. That makes it easier to reply to each of them in more detail.

Answer

zu 1)  ist okay. Man kann auch sagen: Ich kann es; Ich bin Experte darin. Ich beherrsche es (die Sache). "Vertraut" bedeutet so viel wie: Ich habe davon schon mal gehört, aber können tue ich es nicht richtig. 
zu 2) beide ergänzen sich. Besser: Sie ergänzen sich. Wir ergänzen uns (sehr gut); je nach Kontext.

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