I am trying to translate what directly from norwegian to english will be "separate the shit from the cinnamon", in the meaning of separating the good from the bad. Is there a common english frase for what I am trying to say?
I wouldn't call it that erudite. Like many of our most expressive idioms, it's Biblical. But it's certainly in colloquial usage - in, for example, the Crosby, Stills, Nash and Young song 'Almost Cut My Hair'. Another possibility, also Biblical, is 'separate the sheep from the goats'.
Another one, which doesn't mean quite the same, is 'separate the men from the boys' (but that means making distinctions on grounds of age/ability/maturity/experience). I've also heard 'separate the gold from the dross', but that is a bit mannered.