Он дважды сказал неправду.

Сказал is the past tense masculine singular form of сказать, which means to say / to tell in the perfective aspect.

• сказать = to say something once, as a completed act
• сказал = he said

The -л marks past tense, and the masculine form has no extra ending after it:

• сказал = he said
• сказала = she said
• сказало = it said
• сказали = they said

Because он is masculine, сказал is the correct form.

This is about aspect and meaning.

• сказать usually means to say something as a complete, single act
• говорить usually means to speak / to talk / to say in a more general, ongoing, or repeated sense

In this sentence, the idea is that he told a lie twice, with each act viewed as completed. So сказал fits better.

Compare:

• Он дважды сказал неправду. = He told an untruth twice / He lied twice.
• Он говорил неправду. = He was speaking untruthfully / He used to say untrue things.

So сказал sounds more natural here because it refers to distinct completed occasions.

Yes. Дважды means twice, and два раза also means two times.

So these are both possible:

• Он дважды сказал неправду.
• Он два раза сказал неправду.

The difference is mostly style:

• дважды is a bit more compact and slightly more formal or literary
• два раза is very common in everyday speech

English works similarly:

• twice sounds a bit neater
• two times is more literal

Because неправду is the accusative case, and it is the direct object of сказал.

The dictionary form is:

• неправда = untruth / lie

But after a verb like сказать when it means say/tell something, the noun goes in the accusative:

• сказать правду = to tell the truth
• сказать неправду = to tell an untruth / to lie

So:

• nominative: неправда
• accusative: неправду

This is a very common pattern in Russian.

They are close, but not always identical in tone.

• неправда literally means untruth
• ложь means lie / falsehood

In many contexts they overlap, but неправда can sometimes sound a little softer or less abstract than ложь.

For example:

• Это неправда. = That’s not true.
• Это ложь. = That’s a lie.

In your sentence, сказать неправду is a very natural expression meaning to tell a lie or to say something untrue.

Yes. A very common alternative is:

• Он дважды солгал.

Here:

• солгать = to lie (perfective)
• солгал = he lied

This is shorter and very natural.
But сказать неправду and солгать are both good.

A rough comparison:

• сказать неправду = to say something untrue
• солгать = to lie

Sometimes сказать неправду can sound a little less direct or a little softer than солгать, depending on context.

Because неправда is a regular noun meaning untruth / lie.

• правда = truth
• неправда = untruth / falsehood / lie

Written as one word, it is a lexical item with its own meaning.

Sometimes Russian can write не separately for contrast or emphasis, but here the normal form is definitely неправду as one word.

So:

• сказать неправду = standard expression
• сказать не правду = unusual in this sentence unless there is some strong contrast

Yes. Russian word order is more flexible than English word order.

The neutral order here is:

• Он дважды сказал неправду.

But you could also hear:

• Он сказал неправду дважды.
• Неправду он сказал дважды.
• Дважды он сказал неправду.

These versions can shift emphasis:

• Он дважды сказал неправду. = neutral
• Он сказал неправду дважды. = emphasizes twice
• Неправду он сказал дважды. = emphasizes the lie / untruth
• Дважды он сказал неправду. = emphasizes the frequency from the start

Russian uses word order partly for information focus, not just grammar.

Russian often can drop subject pronouns, but in the past tense it depends on clarity and context.

Because сказал already shows masculine singular past, a speaker may omit он if it is obvious who is being talked about:

• Дважды сказал неправду. = He said an untruth twice, if the subject is clear from context

However, including он is very normal and often clearer, especially for learners or in isolated sentences.

So:

• Он дважды сказал неправду. = complete, clear sentence
• Дважды сказал неправду. = possible in context

Он is in the nominative case, because it is the subject of the sentence.

Cases here:

• он = nominative, subject
• неправду = accusative, direct object

So the structure is:

• Он = he
• дважды = twice
• сказал = said
• неправду = an untruth / a lie

Yes, it is natural and correct.

It sounds a little more neutral or bookish than the shorter:

• Он дважды солгал.

But Он дважды сказал неправду is absolutely normal Russian and easy to understand. It may even sound slightly less harsh than directly saying солгал.

So it is a good sentence both grammatically and stylistically.