Ons sal seker môre vroeg vertrek.

A word-by-word breakdown is:

• Ons = we
• sal = will
• seker = probably / likely in this sentence
• môre = tomorrow
• vroeg = early
• vertrek = leave / depart

So the structure is basically:

subject + future/modal verb + sentence adverb + time expression + main verb

Because Afrikaans main clauses usually put the finite verb in second position.

Here, sal is the finite verb, so it has to come right after the subject:

• Ons sal ...

The main verb vertrek then goes to the end in its base form.

So:

• Ons vertrek môre vroeg. = We leave early tomorrow.
• Ons sal môre vroeg vertrek. = We will leave early tomorrow.

This is very normal Afrikaans word order with modal verbs like sal, kan, moet, wil, etc.

After modal verbs such as sal, Afrikaans uses the bare infinitive.

So you say:

• Ons sal vertrek
• Ek kan swem
• Hy moet werk

not:

• Ons sal te vertrek ✘

You do use te in other constructions, for example:

• om vroeg te vertrek = to leave early

So after sal, no te is needed.

Yes, seker can be a little tricky for English speakers.

In many statements, seker often means probably, likely, or I suppose rather than certainly.

So here:

• Ons sal seker môre vroeg vertrek

most naturally means something like:

• We’ll probably leave early tomorrow.

If you want to say definitely / certainly, Afrikaans often uses words like beslis.

So seker is a bit of a false friend: it does not always mean English sure.

Afrikaans can often use the present tense for future meaning if the time is already clear.

So these can both work:

• Ons sal môre vroeg vertrek.
• Ons vertrek môre vroeg.

Because môre already shows that the action is in the future, the second version is perfectly natural.

Using sal can make the future meaning more explicit, and sometimes it sounds a bit more like a prediction or intention.

Both can refer to the future, but they are not always identical.

• sal = will
• gaan = often closer to going to

So you could also say:

• Ons gaan môre vroeg vertrek.

That sounds very natural too, often a bit more conversational and plan-like.

Very roughly:

• sal = neutral future / prediction
• gaan = going to / planned future / more immediate feel

In many everyday situations, both are possible.

môre vroeg is a very natural neutral order: tomorrow early = early tomorrow.

Afrikaans often places the broader time word first and the more specific time detail after it:

• môre vroeg = tomorrow, early

You can move time expressions around for emphasis, for example:

• Môre vroeg sal ons vertrek.

That is also correct. But in the original sentence, môre vroeg is the most straightforward order.

Yes, vroeg is an adverb here, because it tells you how/when the leaving happens.

Afrikaans usually does not add a special ending like English -ly.

So the same word can often serve as adjective or adverb:

• ’n vroeë trein = an early train
• Ons vertrek vroeg = We leave early

That is very common in Afrikaans.

vertrek means to depart, to leave, or to set off.

It is used for leaving a place, starting a journey, or departing somewhere.

So:

• Ons vertrek môre. = We leave tomorrow.

It does not usually mean leave something behind in the English sense, like:

• I left my keys at home.

For that idea, Afrikaans would use other verbs such as los or agterlaat, depending on the context.

The ô is part of the normal spelling and marks a particular vowel quality. It is not silent.

A rough English-friendly guide is something like MOR-uh or MOH-ruh, though exact pronunciation depends on accent.

The important point for a learner is:

• learn môre as a fixed word
• do not pronounce it exactly like English more

The accent mark is there to help show that the vowel is different from a plain o.

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

• Sal ons seker môre vroeg vertrek?

For a negative sentence, Afrikaans normally uses double nie:

• Ons sal seker nie môre vroeg vertrek nie.

That double nie ... nie pattern is one of the most important features of Afrikaans negation.