My oë is oop, maar my mond is vol tandepasta wanneer ek my tande borsel.

Because in Afrikaans, the present tense of to be is always is, no matter whether the subject is singular or plural.

So you get:

• Ek is — I am
• Jy is — you are
• Hy/sy is — he/she is
• Ons is — we are
• Hulle is — they are
• My oë is oop — my eyes are open

Unlike English, Afrikaans does not change the form to am / is / are.

Oë means eyes. The singular is oog (eye).

The two dots in oë are called a diaeresis. They show that the vowels are pronounced separately, rather than as one combined sound.

• oog = eye
• oë = eyes

This spelling helps you see that the plural is not pronounced like a single vowel combination.

Oop is simply the adjective open.

So:

• die deur is oop — the door is open
• my oë is oop — my eyes are open

You would not use geoop here. Afrikaans often uses a simple adjective after is to describe a state.

Because my in Afrikaans can mean my in the possessive sense, just like in English.

So in this sentence:

• my oë = my eyes
• my mond = my mouth
• my tande = my teeth

It is the normal possessive adjective, not the object pronoun me.

There is a word for are in meaning, but it is still is.

Afrikaans uses is for both singular and plural in the present tense. So:

• my eyes are open becomes my oë is oop
• my mouth is full becomes my mond is vol

English changes the verb, but Afrikaans does not.

Vol means full, so vol tandepasta means full of toothpaste.

Afrikaans often says this without a separate word for of:

• vol water — full of water
• vol sand — full of sand
• vol tandepasta — full of toothpaste

So the structure is more direct than in English.

Maar means but.

It connects the two contrasting parts:

• My oë is oop — My eyes are open
• maar my mond is vol tandepasta — but my mouth is full of toothpaste

So the sentence is showing a contrast between the eyes being open and the mouth being full of toothpaste.

Afrikaans often forms compound nouns by joining words together.

Here:

• tande = teeth
• pasta = paste
• tandepasta = toothpaste

This is very common in Afrikaans, just as in Dutch and German. English sometimes writes similar ideas as one word too, like toothpaste.

Because wanneer introduces a subordinate clause, and in Afrikaans subordinate clauses usually send the verb to the end.

So:

• Main clause: Ek borsel my tande — I brush my teeth
• Subordinate clause: wanneer ek my tande borsel — when I brush my teeth

This verb-final pattern is one of the most important word-order rules in Afrikaans.

Wanneer means when.

So:

• wanneer ek my tande borsel = when I brush my teeth

In everyday Afrikaans, people also often use as for when in many contexts:

• as ek my tande borsel

Both can work, but wanneer can sound a bit more explicitly like when.

Because tande is the plural of tand.

• tand = tooth
• tande = teeth

Since you normally brush more than one tooth, Afrikaans uses the plural:

• ek borsel my tande — I brush my teeth

Borsel means brush.

So:

• ek borsel my tande = I brush my teeth

This is completely understandable and correct. You may also hear poets in Afrikaans for cleaning or brushing teeth:

• Ek poets my tande

Both are used, though borsel matches the physical action of brushing very clearly.

A more word-for-word version would be:

My eyes is open, but my mouth is full toothpaste when I my teeth brush.

Of course, natural English would be:

My eyes are open, but my mouth is full of toothpaste when I brush my teeth.

This literal version helps show two key Afrikaans features:

• is stays the same even with a plural subject
• in the wanneer clause, the verb borsel comes at the end

A rough guide for an English speaker:

• oë — something like OO-uh or OH-uh, with two syllables
• mond — like English mont or mohnt, with a rounded o
• borsel — roughly BOR-sel

A few pronunciation notes:

• Afrikaans r is usually rolled or tapped more than in English
• the o sound in Afrikaans is often rounder than in English
• oë must be pronounced as two vowel sounds, not one

Yes, it is natural and understandable.

It uses very normal Afrikaans grammar:

• My oë is oop
• maar my mond is vol tandepasta
• wanneer ek my tande borsel

A speaker might also phrase it slightly differently depending on style, but this sentence is perfectly good Afrikaans.