Κάθε Σάββατο η πλατεία είναι τόσο ζωντανή που νιώθω σαν να είμαι σε νησί στις διακοπές.

Κάθε Σάββατο literally means every Saturday.

• Κάθε = every / each
• Σάββατο = Saturday (neuter, singular form)

In Greek, when you use κάθε with a time word (κάθε μέρα, κάθε βράδυ, κάθε Σάββατο, etc.), you normally do not use an article. So you don’t say κάθε το Σάββατο, just κάθε Σάββατο.

The whole phrase functions as a time expression: when? → every Saturday.

Η πλατεία is in the nominative case because it is the subject of the verb είναι (is).

• η πλατεία = the square (subject → nominative)
• την πλατεία would be accusative, used for a direct object, e.g.
  
  • Βλέπω την πλατεία. = I see the square.

In the sentence η πλατεία είναι τόσο ζωντανή, the square is doing the being → so nominative: η, not την.

Yes, you can say both:

• Κάθε Σάββατο η πλατεία είναι τόσο ζωντανή…
• Η πλατεία είναι τόσο ζωντανή κάθε Σάββατο…

Both are correct and natural. The difference is mainly in emphasis:

• Κάθε Σάββατο η πλατεία… puts more emphasis on the time (every Saturday, specifically then).
• Η πλατεία είναι τόσο ζωντανή κάθε Σάββατο… presents the square first and then adds when this happens.

Semantically they’re the same; it’s a stylistic choice.

This is a common Greek pattern:

τόσο + adjective + που + clause
= so + adjective + that + clause

Here:

• τόσο ζωντανή = so lively
• που νιώθω… = that I feel…

So η πλατεία είναι τόσο ζωντανή που νιώθω… means
the square is so lively that I feel…

Adjectives in Greek agree with the noun in:

• gender (masculine / feminine / neuter)
• number (singular / plural)
• case (here: nominative)

πλατεία is feminine, singular, nominative → η πλατεία.

So the adjective must also be:

• feminine
• singular
• nominative

That form is ζωντανή (lively).

Other forms would be:

• masculine: ζωντανός (e.g. ζωντανός δρόμος)
• neuter: ζωντανό (e.g. ζωντανό μέρος)

Νιώθω and αισθάνομαι often overlap and both can mean I feel.

• νιώθω is very common in everyday speech and can sound a bit more informal / emotional / instinctive.
• αισθάνομαι can sound a bit more formal or slightly more “internal”/psychological, though it’s also common.

In this sentence both would work:

• …που νιώθω σαν να είμαι σε νησί…
• …που αισθάνομαι σαν να είμαι σε νησί…

Νιώθω is just a very natural, conversational choice here.

Σαν να + verb is a fixed pattern in Greek meaning as if / like I am / like I were.

• σαν = like / as if
• να είμαι = subjunctive form of είμαι (to be)

You cannot say σαν είμαι in this meaning. You need σαν να + subjunctive:

• νιώθω σαν να είμαι… = I feel as if I am…

Είμαι σαν… also exists but means something else:

• Είμαι σαν νησί. = I am like an island. (a direct comparison, not “as if I were on an island”)

Both are possible, but with slightly different nuances:

• σαν να είμαι σε νησί
  
  • as if I am on an island (current, vivid, immediate feeling)
• σαν να ήμουν σε νησί
  
  • as if I were on an island (a bit more hypothetical / less directly present)

In this context, describing how the square feels right now each Saturday, σαν να είμαι matches the ongoing, vivid feeling.

All are grammatically possible but different in meaning:

• σε νησί
  
  • literally on island, but understood as on an island in a general / vague sense (not a specific island).
• σε ένα νησί
  
  • explicitly on an island (still non-specific, but more “one single island”).
• στο νησί (= σε + το νησί)
  
  • on the island, a specific island known from context.

Here σε νησί is ambiguous on purpose: the person feels as if they are on (some) island, not a particular one.

Both relate to being on vacation / on holidays, but:

• στις διακοπές (σε + τις διακοπές)
  
  • literally in the holidays, often used like English on (my) holidays, stressing the holiday period itself.
  • works very naturally with σε νησί: σε νησί στις διακοπές = an island in the holiday period.
• σε διακοπές
  
  • more like (being) on vacation as a state:
    
    • Είμαι σε διακοπές. = I’m on vacation.

In the given sentence, σε νησί στις διακοπές paints the picture of a holiday island, the kind of island you go to for your holidays.

Greek uses the present tense for:

• actions happening now, and
• habitual / repeated actions (similar to English simple present).

Here:

• Κάθε Σάββατο η πλατεία είναι…
  → Every Saturday, the square is (habitually) lively.
• νιώθω
  → I (regularly) feel that way (whenever this happens).
• σαν να είμαι…
  → as if I am (in those moments).

So the present fits a regular, repeated situation perfectly.

All three can express comparison or similarity, but they’re used slightly differently:

• σαν
  
  • very common, neutral: νιώθω σαν να είμαι σε νησί.
• λες και
  
  • colloquial, often interchangeable with σαν να:
    
    • νιώθω λες και είμαι σε νησί. (no να here)
• όπως
  
  • more “the way that / as”, often for manner:
    
    • Κάν’ το όπως σου είπα. = Do it as I told you.

In this particular sentence, σαν να είμαι (or λες και είμαι) is natural; όπως would not be used with this “as if I were…” meaning.

• νιώθω → [NÝO-tho]

  • stress on the first syllable: ΝΙ‑ώ‑θω (written: νΙώθω)
  • the νι
    • ιώ is pronounced like nyo in English “canyon” + “yo”: one blended sound.

• πλατεία → [pla-TEE-a]

  • stress on the second syllable: πλα‑ΤΕΙ‑α (written: πλατΕια)
  • ει is pronounced like English “ee”.

So you get: ΚΆ-θε SÁ-va-to i pla-TÍ-a í-ne TÓ-so zo-nda-NÍ pu NÝO-tho san na Í-me se ni-SÍ stis dya-ko-PÉS (approximate syllable breakdown with main stresses capitalized).