Po tej bramce część kibiców siedziała cicho, a inni zaczęli jeszcze głośniej kibicować.

In this sentence, po means after in a time/event sense: after that goal.

When po has this meaning, it takes the locative case, so:

• ta bramka = that goal
• po tej bramce = after that goal

So the form is not the basic dictionary form anymore. That is why you see:

• tej instead of ta
• bramce instead of bramka

This is a very common pattern in Polish:

• po meczu = after the match
• po przerwie = after the break
• po tej bramce = after that goal

Because po with the meaning after requires the locative, not the instrumental.

For a feminine noun like bramka, the locative singular is:

• ta bramka
• tej bramce

The form tą bramką is instrumental, which would be used in other kinds of structures, not here.

So:

• po tej bramce = correct
• po tą bramką = incorrect
• po tą bramką may sound tempting to learners because of the ending, but it is not the case required by po in this meaning

Yes. In sports, especially football/soccer, bramka commonly means a goal.

There are a few related meanings:

• brama = gate
• bramka = little gate / goal / goal frame, depending on context

In football language, strzelić bramkę means to score a goal.

So in this sentence, po tej bramce means after that goal, not after that gate.

Because the grammatical subject is część (part, a part, some), and część is singular.

So the verb agrees with część, not with kibiców:

• część = singular feminine noun
• therefore: część ... siedziała

Even though kibiców refers to many fans, the core grammatical subject is still część.

This is similar in English to how we can say part of the crowd was quiet. Polish handles it grammatically as singular here.

Because część works like part of.

So:

• część = part
• część kibiców = part of the fans / some of the fans

After nouns like część, Polish commonly uses the genitive:

• część ludzi = some of the people
• część uczniów = some of the students
• część kibiców = some of the fans

So kibiców is genitive plural of kibic.

Inni means others here and acts as the subject of the second clause:

• a inni zaczęli... = and others began...

Because it is the subject, it is in the nominative plural:

• inni = nominative plural

You would use innych in other roles, for example:

• widzę innych kibiców = I see other fans

As for drudzy/drugich, that usually means the second ones or can sound more contrastive/order-based. In this sentence, inni is the natural word for others.

Zaczęli is the past tense plural form of zacząć (to begin, to start).

It is used because the subject is inni = others.

The ending -li tells you this is the masculine-personal plural past form, which is used for groups containing men or for mixed groups of people. Since kibice are people, this is the expected form.

Compare:

• inni zaczęli = other people began
• inne zaczęły = other things began

So the sentence treats inni as a group of people.

This is a very common Polish structure:

• zacząć + infinitive = to begin/start doing something

So:

• zaczęli kibicować = they began to cheer / started cheering

The first verb, zaczęli, tells you about the beginning of the action. The infinitive, kibicować, tells you what action began.

You can compare:

• zaczął mówić = he started speaking
• zaczęli śpiewać = they started singing
• zaczęli kibicować = they started cheering/supporting

Kibicować means to support, to root for, or to cheer on, especially in sports.

In this sentence, because the context is loud fans after a goal, the best natural translation is something like:

• to cheer
• to cheer on their team
• to support the team loudly

A useful grammar point: kibicować often takes the dative for the team/person supported:

• kibicuję Polsce = I support Poland
• kibicują swojej drużynie = they support their team

In your sentence, that dative object is simply not stated, because it is obvious from context.

Because głośniej is the comparative form: more loudly / louder.

So:

• głośno = loudly
• głośniej = more loudly / louder

The sentence is comparing their cheering to how loud it was before. They did not just cheer loudly; they cheered even louder.

That is why głośniej fits naturally.

Here jeszcze means even or still more.

So:

• głośniej = louder
• jeszcze głośniej = even louder

This is a very common pattern in Polish:

• jeszcze szybciej = even faster
• jeszcze lepiej = even better
• jeszcze głośniej = even louder

So jeszcze strengthens the comparison.

Yes, quite literally.

• siedziała = was sitting / sat
• cicho = quietly, in silence

So część kibiców siedziała cicho means something like:

• some of the fans sat quietly
• some of the fans remained quiet

In context, it suggests they were subdued, disappointed, or silent after the goal.

Polish often uses simple physical verbs like siedzieć in natural ways where English might choose a slightly more abstract phrasing like stayed quiet or went silent.

The given word order is natural and emphasizes the sequence of events:

• Po tej bramce = after that goal
• then what happened to one group
• then what happened to the other group

Polish word order is more flexible than English, so variations are possible, for example:

• Część kibiców siedziała cicho po tej bramce, a inni zaczęli jeszcze głośniej kibicować.

That would still be understandable, but the original sounds very natural because it sets the time/context first.

Also, placing inni after a makes the contrast very clear:

• część kibiców ... , a inni ... = some fans ..., while others ...

Not exactly. A often translates as and, but in many sentences it has a slight contrast meaning, closer to:

• while
• whereas
• and on the other hand

So here:

• część kibiców siedziała cicho, a inni zaczęli jeszcze głośniej kibicować

means not just some were quiet and others cheered louder, but also highlights the contrast between the two reactions.

That is why a is better here than plain i.