Po meczu trener powiedział, że to zwycięstwo jest ważne dla całej drużyny.

Because the preposition po normally requires the locative case when it means after.

• mecz = match
• locative singular of mecz = meczu

So:

• po meczu = after the match

The ending -u is normal for some masculine nouns in the locative. You just have to learn the case form together with the noun.

Powiedział is the past tense, 3rd person singular masculine form of powiedzieć (to say / to tell).

It matches trener, which is a masculine singular noun.

So:

• trener powiedział = the coach said

The -ł ending is a very common sign of the masculine singular past tense in Polish.

Compare:

• powiedział = he said
• powiedziała = she said
• powiedziało = it said

This is about aspect and also a difference in meaning.

• powiedzieć is perfective
• mówić is imperfective

Powiedział presents the action as a completed single statement: the coach said something.

Mówił usually suggests:

• he was speaking
• he used to say
• he kept saying

In this sentence, the speaker means one finished act of saying, so powiedział is the natural choice.

Że means that and introduces a subordinate clause.

• trener powiedział, że... = the coach said that...

In English, that is often optional:

• He said that it was important
• He said it was important

In Polish, że is usually expressed in sentences like this, so it is much less optional than English that.

Here to means this.

So:

• to zwycięstwo = this victory

It is pointing to a specific victory, probably the one from the match just mentioned.

This to is not the same as the to used in sentences like:

• To jest ważne = This is important

In your sentence, to directly modifies the noun zwycięstwo.

Because ważne must agree with zwycięstwo.

• zwycięstwo is neuter singular
• adjectives must match the noun in gender, number, and usually case

So:

• masculine: ważny
• feminine: ważna
• neuter: ważne

That is why we get:

• to zwycięstwo jest ważne = this victory is important

Because the preposition dla requires the genitive case.

Base forms:

• cała = whole
• drużyna = team

Genitive singular forms:

• całej
• drużyny

So:

• dla całej drużyny = for the whole team

This is a very useful pattern to remember:

• dla
  • genitive

Examples:

• dla mnie = for me
• dla dzieci = for the children
• dla naszego miasta = for our city

This is a very common question for English speakers.

Polish does not use sequence of tenses in the same way English often does. After a past reporting verb like powiedział, Polish can keep the tense that reflects the actual situation.

So:

• trener powiedział, że to zwycięstwo jest ważne
  = the coach said that this victory is important

This suggests the victory is still important now.

If you said:

• trener powiedział, że to zwycięstwo było ważne

that would suggest it was important at that time, but maybe not now, or that you are presenting it as a past fact.

So jest is very natural if the importance is still true.

Yes. Polish word order is fairly flexible because case endings show grammatical relationships.

The neutral order here is:

• Po meczu trener powiedział, że to zwycięstwo jest ważne dla całej drużyny.

But you could also hear variations such as:

• Trener powiedział po meczu, że to zwycięstwo jest ważne dla całej drużyny.
• Po meczu powiedział trener, że to zwycięstwo jest ważne dla całej drużyny.
  (more stylistic or marked)

Changing the order usually changes emphasis rather than the basic meaning.

• starting with Po meczu emphasizes when
• starting with Trener emphasizes who

Yes, zwycięstwo is a common noun meaning victory.

It is:

• neuter
• usually used as a regular singular countable noun in this meaning

Its ending -o is a strong clue that it is neuter.

Some forms:

• nominative: zwycięstwo
• genitive: zwycięstwa
• locative: zwycięstwie

Because it is neuter, words agreeing with it will also take neuter forms, like:

• to zwycięstwo
• ważne zwycięstwo

A very literal English-style approach might lead a learner toward something unnatural, for example:

• using the wrong case after po
• forgetting że
• using the wrong adjective ending
• backshifting the tense automatically

The natural Polish sentence works because each part follows Polish grammar:

• po
  • locative → po meczu
• completed act of saying → powiedział
• subordinate clause marker → że
• neuter noun agreement → ważne
• dla
  • genitive → dla całej drużyny

So this sentence is a good example of how Polish relies heavily on case and agreement, not just word order.