Learn Dutch: De manager hoopt dat de baas zal kalmeren. - The manager hopes that the boss will calm down.

You could definitely say De manager hoopt erop dat de baas zal kalmeren. However, when a verb with a fixed preposition (like hopen op) is followed directly by a dat clause, the erop becomes optional. It is frequently dropped to keep the sentence simple and less wordy.

Why is the verb order zal kalmeren at the end of the dat clause? Could I say kalmeren zal?

In a subordinate clause (like one starting with dat), the verbs are pushed to the end. When you have an auxiliary verb (zal) and an infinitive (kalmeren), both word orders are grammatically correct. However, putting the conjugated verb first (zal kalmeren) is much more common in everyday spoken Dutch.

Why use zal kalmeren (will calm down) instead of just the present tense kalmeert?

Using the future tense with zullen (zal) emphasizes that the manager is hoping for a specific future change in the boss's mood. However, you can often use the present tense for future events in Dutch: hoopt dat de baas kalmeert is also perfectly correct and sounds very natural.

Is kalmeren just the word kalm turned into a verb?