Powtarzam to wyrażenie kilka razy, żeby je zapamiętać.

Powtarzam is the 1st person singular present tense form of the imperfective verb powtarzać.

So it means:

• I repeat
• or, depending on context, I am repeating

Polish present tense often covers both the simple present and the present continuous that English separates.

Because wyrażenie is a neuter noun.

In Polish, words like this must agree with the noun’s gender:

• ten for masculine
• ta for feminine
• to for neuter

So:

• ten wyraz = this word
• ta fraza = this phrase
• to wyrażenie = this expression

It actually is in the accusative, because it is the direct object of powtarzam, but for many neuter singular nouns, the nominative and accusative look the same.

So in this sentence:

• to wyrażenie is the object
• its case is accusative
• but its form is identical to the dictionary form

That is very normal in Polish.

Wyrażenie means expression.

It usually refers to:

• a phrase
• a set way of saying something
• a meaningful expression rather than just one word

Compare:

• słowo / wyraz = word
• wyrażenie = expression
• zdanie = sentence

So if the learner is repeating a whole expression, wyrażenie is a good choice.

Kilka means a few or several.

The word raz means time in the sense of one occurrence. After quantity words like kilka, Polish uses the appropriate counted form, here razy.

So:

• raz = once / one time
• dwa razy = two times
• kilka razy = several times

This whole phrase works like an adverb: several times.

Żeby introduces a purpose clause.

Here it means something like:

• so that
• in order to

So:

• Powtarzam to wyrażenie kilka razy, żeby je zapamiętać.
• I repeat this expression several times in order to memorize it.

A more formal alternative is aby, but żeby is extremely common in everyday Polish.

Because the second verb, zapamiętać, also needs its own object.

In other words:

• to wyrażenie is the object of powtarzam
• je is the object of zapamiętać

English does the same thing:

• I repeat this expression several times to memorize it

You would not normally say to memorize with no it if you want the object to be explicit.

Because wyrażenie is neuter singular, and the matching accusative pronoun is je.

Compare:

• masculine: go
• feminine: ją
• neuter: je

So:

• Mam wyrażenie. Powtarzam je.
• I have an expression. I repeat it.

Even though je can also appear in plural contexts, here it is clearly singular neuter, referring to wyrażenie.

This is about aspect, which is very important in Polish.

• zapamiętać is perfective
• pamiętać is imperfective

Here, zapamiętać means something like:

• to memorize
• to commit to memory
• to manage to remember

It focuses on the result.

By contrast, pamiętać usually means:

• to remember
• to have in memory

So repeating something several times is done to achieve the result of memorizing it, which is why zapamiętać fits better.

Because the sentence combines:

• an ongoing/repeated action: powtarzam
• a desired completed result: zapamiętać

So the logic is:

• I keep repeating → imperfective
• until I memorize it / so I can memorize it → perfective

This combination is very natural in Polish: an imperfective main action used to reach a perfective goal.

Yes.

In Polish, a subordinate clause introduced by żeby is normally separated with a comma.

So this is correct:

• Powtarzam to wyrażenie kilka razy, żeby je zapamiętać.

The comma is standard Polish punctuation here.

Yes, Polish word order is fairly flexible, but the original sentence sounds neutral and natural.

For example:

• Powtarzam to wyrażenie kilka razy, żeby je zapamiętać.
  neutral

• To wyrażenie powtarzam kilka razy, żeby je zapamiętać.
  puts more emphasis on this expression

Also, in the second part, żeby je zapamiętać sounds more natural than żeby zapamiętać je, because short pronouns like je often come before the infinitive.

So the given word order is a very good standard version for learners.