Sy sit die salf op die wond sodat dit beter word.

In this sentence, sit means put / place.

That is a very common Afrikaans use of sit:

• Sit die boek op die tafel. = Put the book on the table.
• Sy sit die salf op die wond. = She puts the ointment on the wound.

So Afrikaans sit can mean:

• to sit
• to put / place

The meaning depends on context. Here, because there is a direct object (die salf) and a place (op die wond), it clearly means puts/applies rather than sits.

Yes. In fact, smeer is often a very natural verb for ointment, cream, lotion, or paint.

• Sy smeer die salf op die wond. = She applies/spreads the ointment on the wound.

The difference is roughly:

• sit = put/place
• smeer = smear/spread/apply

So sit is understandable and idiomatic, but smeer is often more specific for something like ointment.

Because die is the Afrikaans definite article, meaning the.

In Afrikaans, die is used for:

• singular nouns
• plural nouns
• all genders

So:

• die salf = the ointment
• die wond = the wound

Unlike English, Afrikaans does not change the article for gender, and unlike some other languages, it does not have different forms like the masculine / feminine / neuter.

Op means on / onto.

So:

• op die wond = on the wound

This fits the physical idea of putting ointment onto the surface of the wound.

Afrikaans often uses op in this kind of expression:

• sit botter op die brood = put butter on the bread
• plak dit op die muur = stick it on the wall

Sodat means so that, in order that, or sometimes so that as a result.

In this sentence:

• Sy sit die salf op die wond sodat dit beter word.
• She puts the ointment on the wound so that it gets better.

It introduces a purpose or result clause.

A very important grammar point is that sodat is a subordinating conjunction, so it changes the word order in the clause that follows.

Because after sodat, Afrikaans uses subordinate-clause word order, where the finite verb usually goes to the end.

So:

• main clause: Sy sit die salf op die wond
• subordinate clause: sodat dit beter word

That is why word comes last.

Compare:

• Dit word beter. = It gets better.
  
  • normal main clause word order
• ... sodat dit beter word. = ... so that it gets better.
  
  • subordinate clause, verb at the end

This is a very important Afrikaans pattern:

• omdat hy moeg is = because he is tired
• dat sy kom = that she is coming
• sodat dit beter word = so that it gets better

Here, dit most naturally refers to the wound, or more loosely the condition of the wound.

So:

• die wond = the wound
• dit beter word = it gets better

Even though English speakers may want to say so that the wound gets better, Afrikaans often uses dit once the thing has already been mentioned.

In Afrikaans, word often means become or get.

So:

• beter word = get better / become better

This is different from English word. It is not a noun here. It is a verb.

Examples:

• Hy word moeg. = He gets tired.
• Dit word koud. = It is getting cold.
• Die wond word beter. = The wound gets better.

So in your sentence, dit beter word means it gets better.

Because is beter and word beter do not mean exactly the same thing.

• is beter = is better
  This describes a state.
• word beter = gets better / becomes better
  This describes a change.

In your sentence, the ointment is being applied with the hope that the wound will improve, so word is the natural choice.

Compare:

• Die wond is beter. = The wound is better.
• Die wond word beter. = The wound is getting better / gets better.

No. Sy is capitalized here only because it is the first word of the sentence.

Normally it is written:

• sy = she / her

Afrikaans does not capitalize it for ordinary politeness. At the start of a sentence, it becomes Sy, just like English She.

A rough pronunciation guide is:

• Sy ≈ say (but shorter)
• sit ≈ sit
• die ≈ dee
• salf ≈ sahlf
• op ≈ op
• die ≈ dee
• wond ≈ vont or vawnt depending on accent
• sodat ≈ soo-dat
• dit ≈ dit
• beter ≈ bay-ter
• word ≈ vurt / vord depending on accent

A rough full version: Say sit dee sahlf op dee vont soo-dat dit bay-ter vurt.

A few useful pronunciation notes:

• w in Afrikaans is usually like English v
• g is often a guttural sound, but there is no g in this sentence
• r may be rolled or tapped, depending on accent

The structure is:

• Sy = subject
• sit = verb
• die salf = direct object
• op die wond = prepositional phrase
• sodat dit beter word = subordinate clause of purpose/result

So the pattern is basically:

Subject + verb + object + prepositional phrase + subordinate clause

That makes the sentence very typical Afrikaans:

• Sy does the action
• sit tells what she does
• die salf is what she puts on
• op die wond tells where
• sodat dit beter word tells why / with what result