Sy verstel die lensopening.

Here Sy means she.

A useful warning for learners: sy can also mean his in other sentences, for example sy kamera = his camera.
In Sy verstel die lensopening, it is clearly the subject pronoun she, because it comes before the verb verstel.

Afrikaans verbs usually do not change form according to the subject in the present tense.

So you get:

• Ek verstel = I adjust
• Jy verstel = you adjust
• Sy verstel = she adjusts
• Ons verstel = we adjust

Unlike English, Afrikaans does not add an extra -s for he/she/it in the present tense.

Verstel usually means adjust, alter, or set differently.

In this sentence, it most naturally means adjusts or is adjusting.

It is often used for changing a setting or position, for example:

• die fokus verstel = adjust the focus
• die stoel verstel = adjust the chair
• die lensopening verstel = adjust the aperture

Die is the definite article, meaning the.

Afrikaans uses die for:

• singular nouns
• plural nouns
• all grammatical genders

So unlike some languages, you do not have to learn different forms of the for masculine, feminine, or neuter nouns.

Here:

• die lensopening = the aperture

Yes, lensopening is one word because Afrikaans often forms compound nouns by joining words together.

Here it is made from:

• lens = lens
• opening = opening

Together, lensopening refers to the aperture or lens opening.

This is very common in Afrikaans. English sometimes writes such combinations as two words, a hyphenated form, or one word, but Afrikaans usually prefers a single compound word.

The sentence follows normal Afrikaans main-clause word order:

Subject + Verb + Object

So:

• Sy = subject
• verstel = verb
• die lensopening = object

This is the same basic order as in English:

She adjusts the aperture.

Yes. The simple present in Afrikaans often covers both meanings, depending on context.

So Sy verstel die lensopening can mean:

• She adjusts the aperture
• She is adjusting the aperture

If the context is about what she is doing right now, English would often prefer is adjusting.
If the context is more general or habitual, English might prefer adjusts.

For a yes/no question, Afrikaans usually puts the verb first:

Verstel sy die lensopening?
= Is she adjusting the aperture? / Does she adjust the aperture?

So the word order changes from:

• statement: Sy verstel die lensopening.
• question: Verstel sy die lensopening?

A rough English-friendly guide would be:

see fer-STEL duh LENS-oh-puh-ning

A few notes:

• Sy sounds roughly like see
• verstel has the stress on the second part: fer-STEL
• die in standard Afrikaans is usually pronounced like duh
• g in opening is not a hard English g sound here; the ending is softer than English learners may expect

Pronunciation varies by speaker and accent, but this guide should help you get close.

Yes, but then the noun would need to be plural:

• die lensopening = the aperture
• die lensopeninge = the apertures

Notice that die stays the same. Afrikaans does not change the word for the between singular and plural.

Not really. It is capitalized here simply because it is the first word of the sentence.

Inside a sentence it would normally be written sy:

• Ek dink sy verstel die lensopening.
  = I think she is adjusting the aperture.

So the capital letter here is just normal sentence capitalization, not a special grammatical form.