Сколько бы слов я ни повторял, я всё равно иногда забываю их.

As a whole, сколько бы ... ни is a very common Russian pattern meaning no matter how many ..., however many ..., or whatever number of ....

In this sentence:

• Сколько бы слов я ни повторял = No matter how many words I repeat

This pattern is often used to introduce a contrast:

• Сколько бы ... ни ..., всё равно ...
• No matter how ..., still ...

So the first clause sets up something that does not change the result in the second clause.

Because бы is a particle that often appears near the beginning of its clause, and in this construction it normally follows the question word:

• сколько бы
• кто бы
• что бы
• где бы
• как бы

So сколько бы is the standard pattern here.

A learner may want to say something like Сколько я бы ни повторял, but that is not the normal form in this structure. Russian strongly prefers:

• Сколько бы слов я ни повторял

So it is best to learn сколько бы ... ни as one chunk.

Because сколько requires the noun to be in the genitive plural.

So:

• слово = singular nominative
• слова = plural nominative
• слов = plural genitive

After words like сколько, Russian uses the genitive plural:

• сколько слов
• много слов
• мало слов

So сколько бы слов is grammatically exactly what we expect.

Here ни is part of the fixed concessive pattern:

• кто бы ... ни
• что бы ... ни
• где бы ... ни
• как бы ... ни
• сколько бы ... ни

It does not mean ordinary negation by itself. Instead, it helps create the meaning no matter ... / however ....

Compare:

• Что бы я ни делал... = Whatever I do...
• Где бы он ни жил... = Wherever he lives...
• Сколько бы слов я ни повторял... = No matter how many words I repeat...

If you used не here, it would not express this pattern correctly. So this is one of those places where you should learn the whole construction as a unit:

• сколько бы + noun + subject + ни + verb

This is because бы in Russian normally combines with a past-tense verb form.

That past form does not always refer to real past time. It is also used for:

• hypothetical situations
• conditional meanings
• generalized statements like this one

So повторял here does not mean the speaker is talking specifically about the past. It is simply the form Russian uses in this kind of бы construction.

You can think of it roughly as something like:

• no matter how many words I may repeat
• no matter how many words I might repeat

Russian expresses that with бы + past-form verb.

Because the sentence is talking about a repeated or ongoing kind of action, not one completed event.

Imperfective fits ideas like:

• repeating again and again
• studying repeatedly
• the process of repetition

So:

• повторял suggests repeated practice or an ongoing effort

That matches the second clause well:

• я всё равно иногда забываю их
• the forgetting happens sometimes, even though the repetition keeps happening

A perfective verb would shift the nuance. For example, повторил would sound more like a completed act or completed amount of repetition, which is less natural in this general statement.

Всё равно means something like:

• all the same
• anyway
• still
• nevertheless

It emphasizes that the result does not change.

So the logic is:

• I repeat the words a lot
• but even so
• I sometimes forget them

The sentence would still be understandable without всё равно, but it would lose some of that strong despite that feeling.

This pairing is very common:

• Как бы он ни старался, всё равно...
• Что бы ты ни говорил, всё равно...
• Сколько бы слов я ни повторял, всё равно...

Because that is a natural place for an adverb of frequency in Russian.

• я всё равно иногда забываю их

This word order is neutral and natural.

Russian word order is flexible, though, so other versions are possible:

• я иногда всё равно забываю их
• я всё равно забываю их иногда

But they may sound a bit different in emphasis or rhythm.

The original version is a very normal way to say it.

Yes, it could move, because Russian word order is flexible.

The original:

• я всё равно иногда забываю их

is a neutral, natural order.

You could also say:

• я всё равно иногда их забываю
• их я всё равно иногда забываю

But the emphasis changes:

• их later in the sentence is fairly neutral
• их earlier gives it more focus or contrast

For example, их я всё равно иногда забываю can sound like those words are what I still sometimes forget.

So the original word order is simply the most straightforward one.

Because the sentence has two clauses:

1. Сколько бы слов я ни повторял
2. я всё равно иногда забываю их

The first clause is a subordinate clause, and the second is the main clause. In Russian, clauses like this are normally separated by a comma.

The first clause gives the concessive idea:

• no matter how many words I repeat

The second gives the main result:

• I still sometimes forget them

So the comma is required.

Yes. Very much so.

This is a productive and common pattern in Russian:

• Кто бы ни...
• Что бы ни...
• Где бы ни...
• Когда бы ни...
• Как бы ни...
• Сколько бы ни...

It is worth learning as a template.

For example:

• Что бы я ни делал, ничего не помогает.
• Как бы он ни объяснял, они не понимают.
• Сколько бы я ни учил, я всё равно ошибаюсь.

If you remember the pattern question word + бы + ... + ни + verb, you will recognize and build many useful Russian sentences.