Ich obrona jest silna, więc trudno strzelać bramki.

Here ich means their:

• ich obrona = their defense

This is one of the Polish possessive forms that does not change its ending. Compare:

• ich obrona = their defense
• ich trener = their coach
• ich drużyna = their team

So unlike mój / moja / moje or twój / twoja / twoje, the form ich stays the same.

Also, ich can mean them in other contexts, but here it is clearly possessive because it comes before a noun: ich obrona.

Because obrona is a feminine singular noun, and the adjective has to agree with it.

• obrona = feminine singular
• silna = feminine singular form of strong

So:

• silny = masculine
• silna = feminine
• silne = neuter

That is why we get:

• Ich obrona jest silna. = Their defense is strong.

Jest is the 3rd person singular of być = to be.

So:

• obrona jest silna = the defense is strong

In standard Polish, you normally use jest in this kind of sentence with an adjective. Leaving it out would sound incomplete, very informal, or stylistically unusual.

So Ich obrona silna is not the normal standard version; Ich obrona jest silna is.

Więc means so, therefore, or thus.

It connects the two parts of the sentence:

• Ich obrona jest silna = Their defense is strong
• więc trudno strzelać bramki = so it is hard to score goals

The comma is normal here because więc introduces the result of the first clause. In Polish, a comma before więc is very common and standard.

Because trudno is part of a very common impersonal pattern:

• trudno + infinitive = it is hard to ...

So:

• trudno strzelać bramki = it is hard to score goals

This does not describe a noun, so you do not use an agreeing adjective like trudny / trudna / trudne.

Compare:

• To jest trudne. = That is difficult.
• Trudno strzelać bramki. = It is hard to score goals.

In English, you need it is. In Polish, you can simply say trudno.

This is about aspect.

• strzelać = imperfective
• strzelić = perfective

In this sentence, strzelać fits because the meaning is general: their defense is strong, so scoring goals in general is difficult.

So:

• trudno strzelać bramki = it is hard to score goals / keep scoring goals

If you used strzelić, it would sound more like to score a goal once or to manage to score:

• trudno strzelić bramkę = it is hard to score a goal

Both can be possible in the right context, but the given sentence is talking about a general situation, so strzelać works well.

Yes. In sports, bramka can mean a goal.

Here bramki is the accusative plural of bramka:

• singular: bramkę
• plural: bramki

Because the sentence means score goals, the noun is the direct object of strzelać.

So:

• strzelać bramki = to score goals

You may also hear strzelać gole, which is also very common in sports Polish. Both are understandable, though gole can sound a bit more directly tied to modern sports usage.

Polish often leaves out information that is obvious from context.

If you already know the topic is their team, then:

• Ich obrona jest silna, więc trudno strzelać bramki.

naturally suggests:

• their defense is strong, so it is hard to score goals against them

If you want to make that explicit, you could say:

• Ich obrona jest silna, więc trudno strzelać im bramki.

Here im means to them / against them in the sports sense.

Ich obrona is the normal, neutral order.

In Polish, possessive words like ich usually come before the noun:

• ich obrona
• ich drużyna
• ich trener

You might sometimes see unusual word order for emphasis, contrast, or style, but for an everyday sentence, Ich obrona jest silna is the standard way to say it.