Η διαδικασία για την αίτηση είναι απλή, αλλά χρειάζεται προσοχή.

Η is the feminine singular definite article, meaning the.

So:

• η διαδικασία = the process

Greek uses the definite article very regularly, often more often than English does. Here it is needed because the sentence is talking about a specific process.

Also, διαδικασία is a feminine noun, so the article must also be feminine singular: η.

It is in the nominative case because it is the subject of the sentence.

In:

• Η διαδικασία ... είναι απλή
• The process ... is simple

the thing being described is η διαδικασία, so it appears in the nominative.

You can also see this from the article:

• η = nominative feminine singular
• την = accusative feminine singular

So the sentence gives you a nice contrast between nominative and accusative later on.

για usually means for and is followed by the accusative case.

So:

• για = for
• την αίτηση = the application (accusative)

That is why you get:

• για την αίτηση = for the application

The article changes to την because αίτηση is feminine singular accusative here.

Because after για, Greek normally uses the accusative.

Compare:

• η αίτηση = the application (nominative, subject form)
• την αίτηση = the application (accusative, object form / after many prepositions)

So:

• η αίτηση είναι έτοιμη = the application is ready
• για την αίτηση = for the application

This is one of the basic patterns learners need to get used to: the article changes with the case.

Because adjectives in Greek must agree with the noun they describe in gender, number, and case.

Here, διαδικασία is:

• feminine
• singular
• nominative

So the adjective must match it:

• απλός = masculine
• απλή = feminine
• απλό = neuter

Therefore:

• Η διαδικασία είναι απλή = The process is simple

είναι is the verb is / are.

Greek, like English, often uses the verb to be to link a subject with an adjective:

• Η διαδικασία είναι απλή = The process is simple

So the structure is:

• subject
  • είναι
    • adjective

Without είναι, the sentence would be incomplete in standard Greek.

Because Greek often leaves out subject pronouns when they are understood from the context.

In English, you would usually say:

• ..., but it requires attention

In Greek, the subject is already clear from the previous clause:

• Η διαδικασία ... αλλά χρειάζεται προσοχή

The verb χρειάζεται is enough here, and Greek does not need to repeat a pronoun like it.

This is very common in Greek and is one of the biggest differences from English.

χρειάζεται is the 3rd person singular form of χρειάζομαι / χρειάζεται in the sense of need / require.

Here it means:

• it needs
• it requires

So:

• χρειάζεται προσοχή = it requires attention / attention is needed

Because the subject is understood to be η διαδικασία, the verb is singular.

Because προσοχή is being used in a general, abstract sense: attention or care.

Greek often omits the article with abstract nouns when speaking generally.

So:

• χρειάζεται προσοχή = it requires attention / care

If you added an article, it would sound more specific, as if you meant a particular kind of attention already known in the context. Without the article, it is the natural general phrasing.

Yes. That is a very natural way to understand it.

Depending on context, χρειάζεται προσοχή can be translated as:

• it requires attention
• care is needed
• you need to be careful

The Greek phrasing is slightly flexible, and English may choose different wordings depending on style.

Because αλλά means but, and it connects two clauses:

• Η διαδικασία για την αίτηση είναι απλή
• αλλά χρειάζεται προσοχή

The comma helps separate the two ideas, just as in English:

• The process for the application is simple, but it requires attention.

This punctuation is normal and standard.

Yes, but it would mean something slightly different.

Compare:

• για την αίτηση = for the application
• της αίτησης = of the application

So:

• η διαδικασία για την αίτηση = the process for the application
• η διαδικασία της αίτησης = the application process / the process of the application

Both can work depending on context, but they are not identical in form or nuance.

A simple pronunciation guide is:

• I diadikasía ya tin eétisi íne aplí, alá chriázetai prosokhí.

A few quick notes:

• η / ι / υ / ει / οι often sound like ee
• για sounds like ya
• χ in χρειάζεται and προσοχή is a rough sound, like the ch in German Bach or Scottish loch
• stress matters in Greek, so pay attention to:
  • διαδικασία
  • αίτηση
  • απλή
  • χρειάζεται
  • προσοχή