Mój kolega wygląda na zmęczonego.

Because mój has to agree with kolega, and kolega is a masculine noun.

Even though kolega ends in -a, it refers to a male person, so it is grammatically masculine. That is why the possessive adjective is:

• mój kolega = my male friend / my colleague

Compare:

• moja koleżanka = my female friend / female colleague
• moje dziecko = my child (neuter)

So the form of mój depends on the grammatical gender of the noun, not just the final letter.

Yes. Kolega is one of those Polish nouns that refer to a man but end in -a.

This is unusual from an English learner’s point of view, because many Polish nouns ending in -a are feminine, but some masculine nouns do this too, especially nouns for male people.

So:

• ten kolega = this male friend/colleague
• mój kolega
• dobry kolega

Not:

• ta kolega
• moja kolega

A very similar pattern exists with words like:

• mężczyzna = man
• poeta = poet
• tata = dad

They may end in -a, but they are grammatically masculine.

In this sentence, wygląda na means looks/seems/appears to be.

So:

• Mój kolega wygląda na zmęczonego = My friend looks tired / My friend seems tired

This is a very common Polish pattern:

• wyglądać na + adjective/noun in the accusative

Examples:

• Wyglądasz na szczęśliwego. = You look happy.
• On wygląda na lekarza. = He looks like a doctor / He seems to be a doctor.

It does not mean physical resemblance only. It often means your impression of someone.

Because wyglądać na is a fixed Polish pattern.

Polish often uses prepositions in places where English does not. In English you simply say looks tired, but in Polish the usual structure is:

• wyglądać na + accusative

So the na is required in this construction.

Compare:

• wygląda na zmęczonego = looks tired
• wygląda na chorego = looks ill
• wygląda na miłego człowieka = seems like a nice person

You should learn wyglądać na as one unit, much like learning an English expression.

Because after wygląda na, Polish uses the accusative case.

The basic dictionary form is:

• zmęczony = tired

But in this sentence it has to match kolega in gender, number, and case. Since kolega is masculine animate, the accusative form is:

• zmęczonego

So:

• On jest zmęczony. = He is tired.
  Here zmęczony is in the nominative.
• On wygląda na zmęczonego. = He looks tired.
  Here zmęczonego is in the accusative after na.

This is one of the important things to notice: Polish often changes adjective endings depending on the structure of the sentence.

No, because kolega is the subject of the sentence, so it stays in the nominative:

• Mój kolega = the one doing the looking/seeming

The phrase after na is separate:

• na zmęczonego = as tired / to be tired-looking

So the sentence has:

• mój kolega — nominative subject
• na zmęczonego — prepositional phrase with accusative

Only the word governed by na changes here, not the subject.

Yes, and the difference is important.

• Mój kolega jest zmęczony. = My friend is tired.
  This sounds like a statement of fact.
• Mój kolega wygląda na zmęczonego. = My friend looks tired.
  This means that based on appearance, that is your impression.

So jest zmęczony is stronger and more direct.
Wygląda na zmęczonego is a judgment based on what you see.

In many contexts, English uses looks tired where Polish naturally uses wygląda na zmęczonego.

Not necessarily.

Kolega can mean:

• a male friend
• a buddy
• a classmate
• a colleague
• a male acquaintance, depending on context

It does not always imply a very deep or intimate friendship.

A closer or stronger word is:

• przyjaciel = close friend

So mój kolega can sometimes be better understood as my friend, but in other situations it may be closer to my colleague or my mate/acquaintance.

Yes, Polish word order is more flexible than English word order.

The neutral, most natural version is:

• Mój kolega wygląda na zmęczonego.

But other orders are possible for emphasis, for example:

• Na zmęczonego wygląda mój kolega.
• Wygląda na zmęczonego mój kolega.

These are more marked and would usually depend on context or emphasis. For learners, the original version is the safest and most natural one to use.

A rough pronunciation guide:

• wygląda ≈ vih-GWON-da

A few key sounds:

• ł is pronounced like English w
• ą is a nasal vowel; before d it often sounds somewhat like on or om
• wy- is usually like vih

So wygląda does not sound like the written ł in many other European languages; in modern Polish, ł is basically a w sound.

Wyglądać is imperfective.

That is the normal verb you use for:

• describing someone’s appearance
• saying how something looks
• making general observations

Examples:

• Wyglądam źle. = I look bad.
• To wygląda dobrze. = That looks good.
• On wygląda na zaskoczonego. = He looks surprised.

In this kind of sentence, learners usually just need to remember wyglądać na + accusative as the standard pattern.