a criminal case that has not been solved for a long time
ein Kriminalfall, der schon lange ungelöst ist (ein kriminalfall, der schon lange ungelost ist)
"The detective reopened a cold case from 1999."
"Der Detektiv öffnete einen Cold Case aus dem Jahr 1999 erneut." (Der Detektiv offnete einen cold case aus dem jahr 1999 erneut)
to discuss ideas casually
something that completely changes the way things are done
a small sign of possible success or improvement
to reduce the level or amount of something
to shift responsibility to someone else.
to solve a complex problem or mystery