Nevím, jestli zítra pojedu autobusem, nebo půjdu pěšky.

In Czech, subject pronouns are often omitted because the verb ending already shows the person.

• Nevím = I don’t know
• the ending -ím tells you it is I

So Já nevím is possible, but já is usually unnecessary unless you want emphasis, contrast, or emotional stress.

• Nevím... = neutral
• Já nevím... = I don’t know / as for me, I don’t know

Jestli means whether / if in indirect questions.

In this sentence:

• Nevím, jestli... = I don’t know whether...

It introduces the idea that the speaker is unsure between two possibilities.

This is different from English if in a condition. Here it does not mean something like if it rains. It means whether.

So:

• Nevím, jestli pojedu... = I don’t know whether I’ll go...

Usually, no, not in normal conversation.

-li is a more formal or literary equivalent of jestli, but it is attached to the first word of the clause:

• Nevím, pojedu-li zítra autobusem...

This sounds formal, written, or old-fashioned. In everyday Czech, jestli is much more natural.

Zítra means tomorrow, and Czech word order is flexible. Its position depends on emphasis and what sounds natural.

Here:

• Nevím, jestli zítra pojedu autobusem, nebo půjdu pěšky.

This is a very natural order, with zítra setting the time early in the clause.

Other word orders are possible, for example:

• Nevím, jestli pojedu zítra autobusem, nebo půjdu pěšky.

That also works. The difference is mainly in emphasis and rhythm, not basic meaning.

Because jet and jít are verbs of motion that can form the future without budu.

So:

• pojedu = I will go / I will travel (by vehicle)
• půjdu = I will go / I will walk

These are future forms, even though they are single-word forms.

This is very common with Czech verbs of motion:

• jedu = I am going / I go by vehicle
• pojedu = I will go by vehicle
• jdu = I am going / I am walking
• půjdu = I will go / I will walk

They come from two different motion verbs and describe different ways of going.

• pojedu comes from jet = to go by vehicle, ride, travel
• půjdu comes from jít = to go on foot, walk

So in this sentence:

• pojedu autobusem = I’ll go by bus
• půjdu pěšky = I’ll go on foot / I’ll walk

English often uses go for both, but Czech makes the distinction very clearly.

Because after a means of transport, Czech often uses the instrumental case.

• autobus = nominative, the basic dictionary form
• autobusem = instrumental

So:

• jet autobusem = to go by bus
• jet vlakem = to go by train
• jet autem = to go by car

The instrumental here expresses the means by which you travel.

Because pěšky is an adverb meaning on foot.

Czech uses different structures for different kinds of movement:

• autobusem = by bus, using the instrumental case
• pěšky = on foot, an adverb

So you simply say:

• jít pěšky = to go on foot / to walk

You do not normally build this with noha here.

Nebo means or. It connects the two alternatives the speaker is deciding between:

• pojedu autobusem
• půjdu pěšky

So the whole sentence presents two possibilities:

• I don’t know whether tomorrow I’ll go by bus, or walk.

This is a straightforward coordinating conjunction.

Yes, sometimes.

• nebo = or
• anebo = or, often a little more explicit or emphatic

In this sentence, both are possible:

• Nevím, jestli zítra pojedu autobusem, nebo půjdu pěšky.
• Nevím, jestli zítra pojedu autobusem, anebo půjdu pěšky.

But nebo is the most neutral and common choice.

Because these particular verbs of motion usually have their own future forms.

You normally say:

• pojedu, not budu jet
• půjdu, not budu jít

Using budu + infinitive is normal for many imperfective verbs, but jít and jet are special and commonly form the future differently.

So:

• budu dělat = I will do
• pojedu = I will go by vehicle
• půjdu = I will go on foot

It can feel slightly repetitive from a grammar point of view, because půjdu already comes from the walking verb jít.

But in natural Czech, půjdu pěšky is completely normal. It makes the contrast with pojedu autobusem very clear:

• by bus
• on foot

So the phrase is not wrong or unnatural at all. In fact, it sounds very natural in this context.

Because one jestli is enough to introduce the whole indirect question, and then nebo links the alternatives.

Structure:

• Nevím = I don’t know
• jestli... nebo... = whether... or...

This works much like English:

• I don’t know whether I’ll go by bus or walk.

You do not need another jestli before půjdu pěšky.

Standard Czech punctuation uses a comma before the subordinate clause introduced by jestli:

• Nevím, jestli...

So that comma should be there.

There is also a comma before nebo here because it connects two finite clauses inside the larger sentence:

• ...pojedu autobusem, nebo půjdu pěšky

So the punctuation in the original sentence is standard and correct.

It has two parts:

1. main clause:

   • Nevím = I don’t know

2. subordinate clause introduced by jestli:

   • jestli zítra pojedu autobusem, nebo půjdu pěšky
   • whether tomorrow I’ll go by bus or walk

So literally, the structure is:

• I don’t know, whether tomorrow I’ll go by bus, or I’ll go on foot.

In natural English, this becomes:

• I don’t know whether I’ll go by bus tomorrow or walk.

It is neutral everyday Czech.

Nothing in it is especially slangy, literary, or highly formal. You could say it in normal conversation without any problem.

Words like Nevím, jestli, zítra, autobusem, and pěšky are all standard and common.

No, that would be wrong or at least very unnatural.

Czech distinguishes between going:

• by vehicle → jet
• on foot → jít

So:

• pojedu autobusem = correct
• půjdu pěšky = correct

But:

• půjdu autobusem = not correct in normal Czech
• pojedu pěšky = also wrong in normal usage

This is one of the important differences from English, where go can cover both ideas.