Iudex dicit poenam nimis duram esse.

Because dicit introduces an indirect statement. In Latin, after verbs like say, think, know, and hear, the reported statement is often expressed with:

• an accusative subject
• an infinitive verb

So in poenam nimis duram esse, poenam is the subject of the reported idea, but it appears in the accusative because of this construction.

For the same reason: this is an indirect statement.

In a direct statement, Latin would say something like:

• Poena nimis dura est = The punishment is too harsh

But after dicit, Latin changes the verb of that statement into an infinitive:

• poenam nimis duram esse = the punishment to be too harsh

That is why est becomes esse.

Because duram agrees with poenam.

Since poenam is:

• accusative
• singular
• feminine

the adjective describing it must match:

• duram = accusative singular feminine

So poenam duram means a harsh punishment or, in this sentence, the punishment [to be] harsh.

It is the accusative-and-infinitive construction, often called an indirect statement.

The pattern is:

• main verb of saying/thinking/etc.
• accusative subject of the reported statement
• infinitive verb of the reported statement

So here:

• Iudex = the judge
• dicit = says
• poenam = the punishment, as accusative subject of the reported statement
• nimis duram = too harsh
• esse = to be

So Latin literally says something like:

• The judge says the punishment to be too harsh

Natural English usually changes that to:

• The judge says that the punishment is too harsh

Because Latin often does not need one in this kind of sentence.

English commonly says:

• The judge says that the punishment is too harsh

But Latin usually expresses this idea with the accusative + infinitive construction instead of using a separate word meaning that.

So dicit does not need a Latin equivalent of that here; the grammar itself shows that a reported statement follows.

Nimis is an adverb meaning too, excessively, or overly.

So:

• dura = harsh
• nimis dura = too harsh

It modifies the adjective duram.

Because Latin word order is much freer than English word order.

Latin often places verbs, especially infinitives like esse, later in the clause. That does not change the meaning. The sentence could be rearranged in other ways and still mean the same thing, though some orders sound more natural than others.

So Iudex dicit poenam nimis duram esse is a normal Latin order.

Iudex is nominative singular, and it is the subject of dicit.

So:

• iudex = judge
• dicit = says

That gives:

• The judge says...

It is important to separate the two subjects in the sentence:

• iudex is the subject of the main verb dicit
• poenam is the subject of the infinitive esse inside the indirect statement

Not in the ordinary sense.

A beginner might think poenam is simply the direct object of dicit, but more precisely it is the accusative subject of the infinitive esse inside the indirect statement.

So the judge is not just saying the punishment; he is saying the punishment to be too harsh, that is, saying that the punishment is too harsh.

The direct statement would be:

• Poena nimis dura est.

That means:

• The punishment is too harsh.

When this becomes indirect after dicit, Latin changes it like this:

• Poena → poenam
• dura → duram
• est → esse

So:

• Poena nimis dura est
  becomes
• Iudex dicit poenam nimis duram esse

Yes.

Latin present tense often covers both a simple present and a progressive present, depending on context.

So dicit can mean:

• says
• is saying

In a basic translation, says is usually the most natural choice.

Because nimis is an adverb, and adverbs commonly come before the adjective they modify.

So:

• nimis duram = too harsh

This is very similar to English word order in phrases like too harsh, very severe, or quite unfair.