Wczoraj spotkałam znajomą na rynku i poszłyśmy razem na kawę.

Because the speaker is female.

In the Polish past tense, the verb agrees with the speaker’s gender in the singular:

• spotkałam = I met said by a woman
• spotkałem = I met said by a man

So this sentence tells us that the person speaking is female.

Because znajomą is in the accusative case, which is used for the direct object of spotkać.

Base form:

• znajoma = a female acquaintance / female friend

After spotkałam:

• spotkałam znajomą = I met a female acquaintance

This is a very common pattern in Polish:

• mam siostrę
• widzę kobietę
• spotkałam znajomą

All of those feminine nouns change in the accusative singular.

Not always. Znajoma usually means a female acquaintance or someone you know. In everyday English, it may sometimes be translated as friend, but it is often less close than a true close friend.

Compare:

• znajoma = female acquaintance / someone I know
• przyjaciółka = female close friend

So in this sentence, znajoma does not necessarily mean a best friend. It simply means a woman the speaker knows.

Because na can mean on / at with the locative case when talking about location.

Here:

• rynek = market square / town square
• na rynku = at the market square

This is a normal Polish expression. For open public spaces like squares, marketplaces, or islands, Polish often uses na rather than w.

So:

• na rynku = at the square / at the market

Also note the case change:

• rynek → rynku in the locative

Very often it means the town square / market square, especially in Polish cities and towns.

Depending on context, rynek can refer to:

• a market
• a central square in town

In this sentence, na rynku will usually be understood as at the town square / market square, not necessarily inside a shopping market building.

Because the group is all female.

In the Polish past tense plural, the verb agrees with the gender of the group:

• poszłyśmy = we went said by a group of females
• poszliśmy = we went if the group includes at least one male

Since the speaker is female and she met znajomą (a female acquaintance), the two people are both female, so:

• poszłyśmy razem na kawę

Because in Polish, going out for a meal or drink is very often expressed with na + accusative.

So:

• iść na kawę = to go for coffee
• iść na herbatę = to go for tea
• iść na lunch
• iść na obiad

Here:

• kawa → kawę in the accusative singular

This is one of those patterns that English speakers simply need to learn as a set expression:

• pójść na kawę = go for coffee

Because na with motion often takes the accusative case when it means going somewhere for a purpose or toward a destination.

Base form:

• kawa

After na in this meaning:

• na kawę

So:

• poszłyśmy na kawę = we went for coffee

This is the same kind of change you see in many feminine nouns ending in -a:

• herbata → na herbatę
• pizza → na pizzę
• kolacja → na kolację

Razem means together.

So:

• poszłyśmy razem na kawę = we went for coffee together

It is not strictly necessary, because poszłyśmy already tells you we went, so togetherness is partly implied. But razem adds emphasis and sounds natural.

Without it:

• Wczoraj spotkałam znajomą na rynku i poszłyśmy na kawę.

This still works perfectly well. Razem just makes it a bit more explicit and natural in conversation.

Because the sentence describes two finished events that happened yesterday:

1. spotkałam = I met
2. poszłyśmy = we went

Both verbs are perfective in meaning here:

• spotkać = to meet, as a completed event
• pójść = to go, as a completed event

That fits very well with wczoraj because the speaker is talking about specific, completed actions in the past.

If you used imperfective verbs, the meaning would change or sound less natural in this context.

Yes. Polish word order is fairly flexible, although some orders sound more natural than others.

This sentence:

• Wczoraj spotkałam znajomą na rynku i poszłyśmy razem na kawę.

could also appear in forms like:

• Spotkałam wczoraj znajomą na rynku i poszłyśmy razem na kawę.
• Na rynku wczoraj spotkałam znajomą i poszłyśmy razem na kawę.

The original version is very natural because it starts with Wczoraj, setting the time immediately.

English speakers should remember that Polish often changes word order for:

• emphasis
• topic/focus
• style

But the original sentence is a very normal neutral order.

At least the first verb would change:

• Wczoraj spotkałem znajomą na rynku...

Then the second verb depends on who we are:

• if the speaker is male and he went with a woman: poszliśmy
• if the speaker is female and went with a woman: poszłyśmy

So a male speaker saying the same thing about himself and a female acquaintance would most naturally say:

• Wczoraj spotkałem znajomą na rynku i poszliśmy razem na kawę.

Because a mixed group takes the masculine personal plural form -liśmy.

Yes, very common.

Polish often uses this structure for social activities:

• iść na kawę = go for coffee
• iść na piwo = go for a beer
• iść na obiad = go for lunch / dinner
• iść na spacer = go for a walk
• iść do kina = go to the cinema

So poszłyśmy razem na kawę is a very natural, everyday phrase.