Я сфотографировала бутон и один белый лепесток, потому что они выглядели очень красиво.

Because the verb is in the past tense, and in Russian past-tense verbs agree with the gender of the speaker when the subject is я.

• Я сфотографировала = I photographed / I took a photo (said by a woman)
• Я сфотографировал = the same thing, but said by a man

So the ending -ла tells you the speaker is female.

Сфотографировать is a perfective verb, and here it makes sense because the sentence talks about a completed action: the speaker took the photo.

Compare:

• Я фотографировала = I was photographing / I used to photograph / I was taking photos
• Я сфотографировала = I photographed / I took a photo (completed)

In this sentence, the person is referring to one finished act, so сфотографировала is the natural choice.

They are actually in the accusative case, because they are the direct objects of сфотографировала.

But for many inanimate masculine singular nouns, the accusative looks exactly the same as the nominative.

So:

• nominative: бутон
• accusative: бутон

and

• nominative: лепесток
• accusative: лепесток

That is why they appear unchanged.

Here один literally means one. It can be used to emphasize that it was one single white petal, not several.

So:

• белый лепесток = a white petal / the white petal
• один белый лепесток = one white petal, one single white petal

Russian has no articles like a or the, so learners sometimes wonder whether один is being used like a. Sometimes it can feel article-like in context, but here it most naturally keeps its real meaning: one.

Because the adjective белый must agree with the noun лепесток in:

• gender: masculine
• number: singular
• case: accusative (which here looks like nominative because the noun is inanimate)

So both words take the masculine singular form:

• белый
• лепесток

If the noun were feminine, neuter, or plural, the adjective would change too.

Because the speaker photographed two things:

• бутон
• один белый лепесток

Russian uses и just like English and.

So the structure is straightforward: I photographed a bud and one white petal...

Because потому что means because, and it introduces a subordinate clause.

Russian normally puts a comma before потому что:

• Я ушёл, потому что устал.
• Она улыбнулась, потому что была рада.

So here:

Я сфотографировала бутон и один белый лепесток, потому что они выглядели очень красиво.

The comma separates the main clause from the reason clause.

Because они refers back to бутон и один белый лепесток together.

Since there are two nouns, Russian uses the plural pronoun:

• бутон = it
• лепесток = it
• бутон и лепесток = они = they

Even though both nouns are masculine singular individually, together they form a plural idea, so они is required.

Because the subject of that clause is они, and выглядели is the plural past tense form of выглядеть.

Compare:

• он выглядел = he/it looked
• она выглядела = she/it looked
• оно выглядело = it looked
• они выглядели = they looked

Since они refers to both the bud and the petal, the verb must be plural.

Because выглядеть here describes a state/appearance, not a completed one-time action.

The idea is: they looked beautiful at that time.

Russian usually uses the imperfective for this kind of description. A perfective verb would not fit naturally here.

So the contrast in the sentence is very normal:

• сфотографировала = completed action
• выглядели = ongoing appearance/state

Because красиво is an adverb, and with выглядеть Russian very often uses an adverb to describe appearance:

• выглядеть красиво = to look beautiful
• выглядеть хорошо = to look good
• выглядеть плохо = to look bad

So in this sentence:

• они выглядели очень красиво = they looked very beautiful

Here красиво does not agree with они, because adverbs do not change for gender, number, or case.

A learner may expect an adjective, but after выглядеть, the adverbial pattern is very common and natural.

Очень means very and intensifies красиво:

• красиво = beautifully / beautiful in appearance
• очень красиво = very beautifully / very beautiful in appearance

So it strengthens the description.

Yes. Russian word order is fairly flexible, though different orders can change the emphasis.

This sentence is neutral and natural:

Я сфотографировала бутон и один белый лепесток, потому что они выглядели очень красиво.

But other orders are possible, for example:

• Потому что они выглядели очень красиво, я сфотографировала бутон и один белый лепесток.
• Я сфотографировала один белый лепесток и бутон, потому что они выглядели очень красиво.

These versions are grammatically possible, but the original sounds like a normal, neutral way to say it.

Because Russian has no articles.

English says things like:

• a bud
• the bud
• a white petal
• the white petal

Russian simply says:

• бутон
• белый лепесток

The exact meaning depends on context. In this sentence, the listener understands from context what things are being talked about.

That is one reason learners sometimes notice words like один and wonder whether they are replacing a/an. Sometimes they can add that kind of nuance, but Russian still does not have true articles.

A little, but not in a problematic way.

Grammatically, они could refer to the two previously mentioned items: бутон and лепесток. That is the obvious reading.

Russian often uses plural pronouns this way when two nouns have just been mentioned. In this sentence, the reference is clear enough from context.

Here are the main forms:

• сфотографировала → сфотографировать = to photograph, to take a photo of
• бутон = bud
• лепесток = petal
• выглядели → выглядеть = to look, to appear
• красиво = beautifully / in a beautiful way / beautifully in appearance
• потому что = because

This is useful because Russian sentences often contain inflected forms rather than the dictionary form you would look up first.

It can mean either in English, depending on context.

• сфотографировать что-то = to photograph something
• also very naturally = to take a photo of something

So in everyday English, I took a photo of the bud and one white petal is often the most natural translation, even though the Russian verb is directly related to photograph.

Formally, yes: красиво is an adverb, so it is closer to beautifully.

But with verbs like выглядеть, English often translates more naturally with an adjective:

• они выглядели очень красиво
  naturally: they looked very beautiful

So the Russian structure uses an adverb, while the best English translation may use an adjective. That mismatch is normal.