Το μάθημα είναι πιο εύκολο απ’ όσο φαίνεται στην αρχή.

Το μάθημα usually means the lesson. Depending on context, μάθημα can also mean class, subject, or course material, but lesson is the most natural choice here.

• το = the
• μάθημα = lesson

Μάθημα is a neuter singular noun, which is why it takes the article το.

Είναι means is and comes from the verb είμαι = to be.

So:

• Το μάθημα είναι... = The lesson is...

This is a very standard Greek sentence pattern:
subject + είναι + adjective/comparison

Yes. Πιο εύκολο means easier.

Greek often forms the comparative with:

• πιο
  • adjective

So:

• εύκολο = easy
• πιο εύκολο = easier / more easy

This is extremely common in modern Greek.

You may also see the one-word comparative ευκολότερο, which also means easier. Both are correct, but πιο + adjective is very common in everyday speech.

Because εύκολο has to agree with μάθημα.

Since μάθημα is:

• neuter
• singular

the adjective also stays:

• neuter singular → εύκολο

So the grammar is:

• το μάθημα → neuter singular
• εύκολο → neuter singular adjective

If the noun were masculine or feminine, the adjective form would change.

Because εύκολα is usually an adverb, meaning easily, not an adjective meaning easy.

Compare:

• Το μάθημα είναι εύκολο. = The lesson is easy.
• Μαθαίνω εύκολα. = I learn easily.

In your sentence, we are describing the lesson, so Greek needs the adjective εύκολο, not the adverb εύκολα.

Here απ’ όσο means than in the sense of than it seems.

It comes from:

• από = from / than
• όσο = as much as / how much / than what

Before a vowel, από is often shortened to απ’, which is why you see:

• απ’ όσο instead of από όσο

In this sentence, πιο εύκολο απ’ όσο φαίνεται means:

• easier than it seems
• literally, something like more easy than it appears

In comparisons like this, Greek often uses όσο after πιο... απ’ when the second part contains a verb.

So:

• πιο εύκολο απ’ όσο φαίνεται = easier than it seems
• πιο δύσκολο απ’ όσο νόμιζα = harder than I thought

This structure is very common and natural in Greek.

Φαίνεται means seems, appears, or sometimes looks.

It comes from the verb φαίνομαι, which means to appear / to seem.

So:

• φαίνεται = it seems / it appears

A very natural English translation of the whole part is:

• than it seems
• or than it looks

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

English says:

• it seems

Greek can simply say:

• φαίνεται

The it is not usually stated separately, because Greek does not need it here. The idea is understood automatically.

Στην αρχή means at the beginning or, in this sentence, more naturally at first.

So:

• στην = a contracted form of σε την
• αρχή = beginning

Together:

• στην αρχή = at the beginning / at first

In this sentence, at first is the best English equivalent.

Because σε + την is normally contracted to στην in modern Greek.

This is very common:

• σε το → στο
• σε τη(ν) → στη(ν)

So:

• σε την αρχή becomes στην αρχή

You should think of this as a normal everyday form, not an unusual exception.

The word order is natural, but Greek is more flexible than English.

This sentence is arranged as:

• Το μάθημα = subject
• είναι = is
• πιο εύκολο = easier
• απ’ όσο φαίνεται = than it seems
• στην αρχή = at first

Greek could move στην αρχή earlier for emphasis, but the given order sounds very normal and smooth.

Yes. That is a very good translation.

Because φαίνεται can mean:

• seems
• appears
• looks

all of these can work depending on style:

• The lesson is easier than it seems at first.
• The lesson is easier than it looks at first.
• The lesson is easier than it appears at first.

The first two are the most natural in everyday English.