Mi hermano anda diciendo que el examen oral será difícil.

Here anda diciendo means something like has been saying, keeps saying, or is going around saying.

It does not mean your brother is literally walking while speaking. The structure andar + gerund adds the idea that he says this repeatedly, casually, or to different people.

So the sentence has more nuance than a plain Mi hermano dice que....

Both can be followed by a gerund, but they give different shades of meaning:

• estar diciendo = is saying / is in the middle of saying
• andar diciendo = has been saying around, keeps saying, goes around saying

So andar + gerund often suggests a repeated or loosely ongoing action, not just something happening at this exact moment.

In Spain, andar + gerund is very natural and fairly colloquial.

Because after andar in this kind of structure, Spanish uses the gerund:

• andar diciendo
• andar buscando
• andar pensando

So Mi hermano anda decir... would be incorrect.

If you wanted a simpler sentence, you could say:

• Mi hermano dice que el examen oral será difícil.

That is grammatical, but it loses the extra nuance of repetition or going around saying it.

No. In this sentence, andar is not being used literally.

Its original meaning is related to walking or going about, but in expressions like andar diciendo, it works more like an auxiliary verb. It helps create a meaning similar to go around saying in English.

So the focus is on the repeated action of saying something, not on movement.

Que introduces the content of what your brother is saying. In English, it corresponds to that:

• Mi hermano anda diciendo que...
• My brother keeps saying that...

After verbs of saying, thinking, knowing, etc., Spanish very often uses que to introduce the following clause.

Será is the simple future of ser, so here it means will be.

• será difícil = will be difficult

You could also say:

• va a ser difícil

That also means is going to be difficult and is very common in everyday Spanish.

The difference is usually small here:

• será difícil can sound a bit more neutral or compact
• va a ser difícil can sound a bit more immediate or conversational

Also, remember that the Spanish future can sometimes express probability, but in this sentence the most natural reading is a normal future: the oral exam is in the future.

Because ser difícil is the normal way to describe the nature or difficulty of something like an exam, task, or situation.

• El examen será difícil = The exam will be difficult

With estar, the meaning often shifts toward a temporary state or how something is turning out under current circumstances.

For an exam, ser difícil is the standard choice.

Because in Spanish, adjectives usually come after the noun, especially when they classify the type of thing.

So:

• examen oral = oral exam
• clase práctica = practical class
• prueba escrita = written test

Even though English says oral exam, Spanish normally says examen oral.

El shows that this is a specific oral exam, not just any oral exam.

• el examen oral = the oral exam
• un examen oral = an oral exam

So the sentence suggests that the speaker and listener probably know which exam is being talked about.

Because Spanish often leaves out subject pronouns when the subject is already clear.

Here, Mi hermano already tells us who the subject is, so adding él would usually be unnecessary.

Spanish does this much more than English:

• Mi hermano anda diciendo...
• not usually Él mi hermano anda diciendo...

You might use él only for emphasis or contrast.

It can, depending on tone and context.

Very often, andar diciendo suggests that someone is repeating something around, maybe more than the speaker would like. It can sound like:

• he keeps saying
• he’s been going around saying

So it may carry a slight sense of annoyance, criticism, or gossip. But it is not automatically negative every time. Context and tone decide how strong that feeling is.