Ek bly by die huis wanneer dit reën.

Both are possible meanings of bly in Afrikaans.

• bly = stay / remain
• bly = live / reside

In Ek bly by die huis wanneer dit reën, it means stay: the idea is I stay at home when it rains.

Context tells you which meaning is intended. For example:

• Ek bly in Pretoria. = I live in Pretoria.
• Ek bly by die huis vandag. = I’m staying at home today.

Because by die huis is the normal way to say at home.

• by die huis = at home
• in die huis = in the house / physically inside the building

So if you want the general idea of not going out, by die huis is the natural choice. If you specifically wanted to emphasize being inside the building, then in die huis could make sense.

This is just a difference between the two languages. Afrikaans often uses the article where English does not.

So:

• by die huis literally looks like by the house
• but idiomatically it often means at home

This is a good example of why it helps not to translate word-for-word.

It works like English it in it rains or it is raining.

This dit is a dummy subject. It does not refer to a specific thing. Afrikaans normally uses dit in weather expressions:

• Dit reën. = It’s raining.
• Dit sneeu. = It’s snowing.

So wanneer dit reën is exactly the kind of structure an English speaker would expect.

The ë shows that the vowels are pronounced separately.

So reën is not one smooth vowel sound. The diaeresis tells you to read it more like re-en rather than merging the vowels together.

This mark is common in Afrikaans when two vowels next to each other should be pronounced separately.

Because Afrikaans verbs usually do not change according to the subject the way English verbs sometimes do.

Compare:

• ek bly
• jy bly
• ons bly
• hulle bly

The verb stays the same. This is one of the simpler parts of Afrikaans grammar for English speakers.

Yes. That is very natural.

• by die huis = at home
• tuis = at home / home

So these are both good:

• Ek bly by die huis wanneer dit reën.
• Ek bly tuis wanneer dit reën.

The version with tuis is a bit shorter and very common.

Sometimes, yes, but the meaning can shift slightly.

• wanneer clearly means when
• as can often mean if, and in some contexts also when

So:

• Ek bly by die huis wanneer dit reën. = clearly I stay at home when it rains
• Ek bly by die huis as dit reën. can sound more like I stay at home if/when it rains

If you want the clearest direct match for English when, wanneer is a safe choice.

Yes:

Wanneer dit reën, bly ek by die huis.

That is completely correct.

Notice what happens in the main clause after the fronted time clause:

• not Wanneer dit reën, ek bly by die huis
• but Wanneer dit reën, bly ek by die huis

Afrikaans keeps the finite verb in the second position of the main clause, so bly comes before ek there.

Yes. Afrikaans often uses the simple present in this kind of general statement.

• dit reën can mean it rains or it is raining, depending on context
• Ek bly by die huis wanneer dit reën expresses a general habit or usual situation

So the Afrikaans sentence is normal and natural even though English can phrase the idea in more than one way.