Learn Turkish: Acil bir durumda hemen polisi aramak lazım. - In an emergency, it is necessary to call the police immediately.

In Turkish, when you have an adjective (like acil, meaning "urgent") and the indefinite article bir ("a/an"), bir goes between the adjective and the noun. So "an urgent situation" is Acil bir durum.

Why does it say polisi instead of just polis?

Polisi has the accusative case ending -i because "the police" is the specific direct object of the verb aramak (to call). Since you are calling a specific, known entity (the police), you must use the accusative case here.

Who is supposed to call the police in this sentence?

This sentence makes a general statement, like "One must call..." or "It is necessary to call...". Because it uses the plain dictionary form aramak (to call) next to lazım (necessary), it applies to anyone in general. If it were directed at you specifically, it would use a personal ending, like araman lazım (you need to call).

I learned before that aramak means "to search". Does it also mean "to call"?

Yes! Aramak is a very common verb that means both "to search / look for" and "to call (on the phone)". The context of an emergency (acil bir durum) makes it clear that we are calling the police, not looking for them.