Learn Russian: Мы постоянно информируем начальство, хотя оно часто критикует нас. - We constantly inform the management, although it often criticizes us.

This is a very common pattern for Russian verbs ending in -овать or -евать. When conjugated in the present tense, the -ова- or -ева- suffix drops out and is replaced by -у- or -ю-. So, информировать becomes информируем (we inform), and критиковать becomes критикует (it criticizes).

Why does the sentence use the neuter pronoun оно (it) to refer to the management?

The Russian word for "management" or "the bosses" is начальство. Because it ends in -о, it is a neuter noun. Even though it represents a group of living people, this specific collective noun is grammatically singular and neuter, so it must be referred to with the neuter pronoun оно.

What case is начальство in here? It looks exactly like the dictionary form.

It is in the accusative case, because it is the direct object of the verb (the entity being informed). It looks exactly like the nominative (dictionary) form because neuter nouns do not change their endings in the accusative case.

How do the words постоянно (constantly) and часто (often) affect the verbs in this sentence?