My hart is gesond.

Yes. My is the possessive word meaning my.

So My hart = my heart.

A useful extra note: in Afrikaans, my can also be the object form me in other contexts, so the exact meaning depends on the sentence. Here, before the noun hart, it clearly means my.

Hart means heart. It is a close relative of English heart, so it is an easy cognate to remember.

The spelling is simpler in Afrikaans:

• English: heart
• Afrikaans: hart

Because Afrikaans and English are related Germanic languages, some very common words look the same.
Here, is is the present-tense form of to be:

• My hart is gesond = My heart is healthy

So in this sentence, is works just like English is.

Gesond means healthy or sound / in good condition, depending on context.

In this sentence, it means healthy:

• My hart is gesond = My heart is healthy

You can also use gesond with people, food, habits, and body parts:

• Ek is gesond = I am healthy
• Gesonde kos = healthy food

Because after is, Afrikaans normally uses the basic adjective form.

So:

• My hart is gesond = correct

But before a noun, Afrikaans often adds -e:

• 'n gesonde hart = a healthy heart

This is a very common pattern:

• after the verb: Die kind is gelukkig
• before the noun: 'n gelukkige kind

So:

• hart is gesond
• gesonde hart

Because English also does not use an article in my heart is healthy.

When you use a possessive word like my, you normally do not also add a or the.

Compare:

• my heart
• not the my heart

The same idea applies in Afrikaans:

• my hart
• not die my hart

No, this is a very basic Afrikaans sentence pattern:

subject + verb + adjective

So:

• My hart = subject
• is = verb
• gesond = adjective/complement

This is very similar to English:

• My heart is healthy

A rough English-friendly guide is:

may hart is khuh-SONT

A few pronunciation notes:

• my is not exactly like English my; it is closer to may with a glide
• hart has a clear h and a short a
• g in gesond is the guttural Afrikaans/Dutch g, a sound English does not really have
• the final d in gesond is often pronounced more like t at the end of the word

So learners often hear gesond approximately like khuh-SONT.

No, not in this sentence.

After is, you should use gesond, not gesonde:

• My hart is gesond = correct
• My hart is gesonde = incorrect

Use gesonde before a noun:

• 'n gesonde hart = correct

Afrikaans does not use grammatical gender the way some other European languages do. So you do not need to learn hart as masculine, feminine, or neuter.

That makes things easier for learners. You mainly just learn the noun itself:

• hart = heart

Yes. Gesond is flexible and can describe many things.

Examples:

• Ek is gesond = I am healthy
• My hart is gesond = My heart is healthy
• Sy het gesonde tande = She has healthy teeth
• Dit is gesonde kos = That is healthy food

So using gesond for hart is completely natural.

Yes, it is grammatical and natural.

It is a simple, clear statement meaning that the heart is healthy. Depending on context, native speakers might also say things like:

• My hart is sterk = My heart is strong
• Ek het 'n gesonde hart = I have a healthy heart

But My hart is gesond is perfectly normal.