Marta dice che al supermercato c’è meno confusione la mattina.

In this sentence, che introduces a full clause: che al supermercato c’è meno confusione la mattina.

After verbs like dire, Italian normally uses che when what follows is a complete statement.

• Marta dice che... = Marta says that...

You would not use di here for this kind of meaning.
Di is used in other structures, but not for introducing a normal reported statement like this one.

Here, che means that.

So:

• Marta dice che... = Marta says that...

Just like in English, that can sometimes feel optional in translation, but in Italian che is normally expressed in this structure.

Al is the contraction of a + il.

• a = to / at
• il = the
• al = to the / at the

So:

• al supermercato = at the supermarket

Because supermercato is a masculine singular noun, it takes il, and a + il becomes al.

Italian often uses a with places when meaning at or to a place, especially in common everyday expressions.

• al supermercato = at the supermarket

You may also sometimes see nel supermercato, but that usually sounds more specifically like inside the supermarket.
By contrast, al supermercato is the normal general way to say at the supermarket.

C’è means there is.

It is made from:

• ci = there
• è = is

So:

• c’è meno confusione = there is less confusion

If you said just è meno confusione, that would be ungrammatical in Italian.
Italian uses c’è / ci sono for there is / there are.

Use c’è with a singular noun or singular idea, and ci sono with a plural noun.

In this sentence:

• confusione is singular
• so Italian uses c’è

Examples:

• C’è meno confusione. = There is less confusion.
• Ci sono meno clienti. = There are fewer customers.

The accent is on è, which is the verb is.

This accent matters because:

• è = is
• e = and

So the accent helps distinguish two different words.

In c’è, the apostrophe shows that ci has been shortened before è.

Meno means less.

So:

• meno confusione = less confusion

It is used to make a comparison, even if the second part of the comparison is not stated explicitly.
The idea is something like less confusion than at other times.

In Italian, meno is the normal word for less.

So:

• meno confusione = less confusion

Italian does not usually form this idea with something like more little confusion.
Just as in English we say less confusion, Italian says meno confusione.

Confusione is generally an uncountable noun here, like confusion in English.

So Italian treats it as a singular mass noun:

• c’è meno confusione = there is less confusion

You are not counting separate confusions; you are talking about the general amount of disorder, crowding, or bustle.

Here, confusione does not only mean mental confusion. It often means:

• disorder
• chaos
• bustle
• crowding
• noise and general busy activity

At a supermarket, meno confusione usually means the place is calmer, less crowded, and less hectic.

Italian often uses expressions like la mattina, il pomeriggio, la sera to mean in the morning, in the afternoon, in the evening.

So:

• la mattina = in the morning

This is a very common time expression. Italian does not always need a separate word corresponding to English in.

Yes. All of these are possible, though they can sound slightly different in tone or style:

• la mattina = in the morning
• di mattina = in the morning / mornings
• al mattino = in the morning, often a bit more formal or literary

In everyday speech, la mattina is very common and natural.

Italian word order is flexible, but the sentence is very natural as written:

• Marta dice che al supermercato c’è meno confusione la mattina.

Putting la mattina at the end clearly tells us when there is less confusion.

You could move it for emphasis, for example:

• Marta dice che la mattina al supermercato c’è meno confusione.

That is also correct, but the original order sounds perfectly normal.

Yes, supermercato is masculine singular.

You can see that from:

• the article il supermercato
• the contraction al supermercato = a + il supermercato

Many Italian nouns ending in -o are masculine singular, although there are exceptions.

Yes. Italian present tense often covers both simple present and present progressive, depending on context.

So Marta dice can mean:

• Marta says
• Marta is saying

In this sentence, Marta says is the most natural translation.

A simple pronunciation guide:

• c’è sounds roughly like cheh
• meno sounds like MEH-no
• confusione sounds roughly like kon-foo-ZYO-neh

A key point: in confusione, the s sounds like a z sound in this context:
kon-foo-ZYO-neh.

Yes. In fact, that is the most likely meaning.

• Marta dice che al supermercato c’è meno confusione la mattina usually means in the mornings, there is less confusion at the supermarket or the supermarket is less busy in the morning.

Italian often uses the singular time expression la mattina to refer to a habitual time period in general.