Přenos telefonního čísla začne zítra.

Because přenos normally takes the idea of transfer of something, and in Czech that of something relationship is usually expressed with the genitive.

So:

• přenos = transfer
• telefonní číslo = phone number
• přenos telefonního čísla = transfer of a phone number

Here, čísla is the genitive singular of číslo, and telefonního matches it in case, gender, and number.

The subject is Přenos telefonního čísla.

So the thing that will begin is the phone number transfer.

This is why the verb is singular:

• Přenos telefonního čísla začne zítra.
• Literally: The transfer of the phone number will begin tomorrow.

Even though there are several words before the verb, the core subject is přenos.

Because začne comes from the perfective verb začít.

In Czech, perfective verbs do not normally have a true present meaning. Their present-form endings are used to express the future.

So:

• začíná = is beginning / begins, from imperfective začínat
• začne = will begin, from perfective začít

That is why začne zítra means will begin tomorrow.

The difference is mainly aspect:

• začne = perfective, focusing on the start as a completed event
• začíná = imperfective, focusing on the process or repeated/ongoing action

In this sentence, začne zítra is the natural choice because it means that the transfer will start tomorrow at some point.

If you said začíná zítra, it would sound less natural in many contexts, though it can appear in certain schedules or announcements. For a simple statement about when something starts, začne is the normal form.

Because Czech does not have articles like the or a/an.

Whether something is understood as the transfer, a transfer, or just transfer depends on context.

So:

• Přenos telefonního čísla začne zítra.

can naturally correspond to English:

• The phone number transfer will begin tomorrow
• or sometimes Phone number transfer will begin tomorrow

English needs an article; Czech usually does not.

Yes. Czech word order is flexible, because grammatical relationships are shown mostly by endings rather than fixed position.

For example, these are possible:

• Přenos telefonního čísla začne zítra.
• Zítra začne přenos telefonního čísla.
• Přenos telefonního čísla zítra začne.

They all mean basically the same thing, but the emphasis changes:

• Přenos telefonního čísla začne zítra. = neutral
• Zítra začne přenos telefonního čísla. = emphasizes tomorrow
• Přenos telefonního čísla zítra začne. = can sound more marked or contrastive

For normal neutral style, the original sentence is very natural.

Because it is a noun phrase made up of:

• telefonního = adjectival form of telefonní = telephone/phone
• čísla = genitive singular of číslo = number

Together:

• telefonní číslo = phone number
• telefonního čísla = of the phone number

So in the full sentence, this is not two separate objects. It is one unit: the transfer of the phone number.

Because it has to agree with čísla.

The base noun is:

• číslo = number

This noun is:

• neuter
• singular
• here in the genitive

The adjective telefonní must match that, so it becomes:

• telefonního

This is normal adjective agreement in Czech.

So:

• nominative: telefonní číslo
• genitive: telefonního čísla

Yes, you could, if the context already makes it clear that you mean a phone number.

• Přenos čísla začne zítra. = The number transfer will begin tomorrow.

But without telefonního, čísla could in theory mean some other kind of number, so the full version is clearer and more precise.

Approximate pronunciation:

• Přenos ≈ przhenos or przhe-nos

The hardest sound here is ř, which is a special Czech sound. It is somewhat like a mix of r and zh (the sound in measure).

A rough learner-friendly breakdown:

• Pře- sounds a bit like przhe-
• -nos sounds like nos

You do not need to master ř immediately to be understood, but it is worth practicing over time because it is a very characteristic Czech sound.

Zítra is an adverb, so it does not change for case.

It simply means tomorrow and can be placed in different parts of the sentence depending on emphasis.

Examples:

• Začne zítra. = It will begin tomorrow.
• Zítra začne. = Tomorrow it will begin.

So unlike nouns and adjectives, zítra stays the same.