Jestli přijdu do kanceláře pozdě, šéf nebude mít dobrou náladu.

Here jestli means if.

It is introducing a condition: If I come to the office late, ...

A useful thing to know is that jestli can also mean whether in other sentences, for example:

• Nevím, jestli přijde. = I don’t know whether he’ll come.

In this sentence, though, it is clearly conditional, so if is the right interpretation.

Yes, in many everyday situations you could hear když instead of jestli.

But there is a nuance:

• jestli is a clear if
• když can mean when or if, and often sounds a bit less precise as a pure condition

So:

• Jestli přijdu do kanceláře pozdě... = If I come to the office late...
• Když přijdu do kanceláře pozdě... can also work in casual speech, but may feel a little closer to when I come late depending on context.

If you want a straightforward conditional meaning, jestli is a very safe choice.

Because přijít is a perfective verb.

In Czech, perfective verbs use their present-tense forms to express the future. So:

• přijdu = I will come / I will arrive

That means:

• přijdu looks present in form
• but its meaning is future

And budu přijít is not correct Czech.

Compare:

• přijdu = I will come / arrive once, as a completed event
• přicházím = I am coming / I come
• budu přicházet = I will be coming / I will come repeatedly

Because Czech often drops subject pronouns when the verb form already shows who the subject is.

Here:

• přijdu already means I will come
• so já is unnecessary unless you want emphasis or contrast

So:

• Jestli přijdu do kanceláře pozdě... = neutral
• Jestli já přijdu do kanceláře pozdě... = more emphatic, like if I come late...

This is very normal in Czech.

Because do means to / into, showing movement toward the inside of a place.

The noun after do takes the genitive case:

• kancelář = office
• do kanceláře = to the office / into the office

This contrasts with location:

• v kanceláři = in the office

So:

• jdu do kanceláře = I’m going to the office
• jsem v kanceláři = I’m in the office

Because do requires the genitive case, and kanceláře is the genitive singular form of kancelář.

Basic pattern:

• nominative: kancelář
• genitive: kanceláře

So after do, you need:

• do kanceláře

This is one of the most common Czech preposition + case combinations to learn:

• do + genitive

Because pozdě is an adverb, and here you need an adverb to describe how you come.

• pozdě = late
• it modifies the verb přijdu

You are not describing a noun, so you do not use an adjective.

Compare:

• přijdu pozdě = I will come late
• pozdní vlak = a late train

So in this sentence, pozdě is exactly the right form.

Because mít is an imperfective verb, and the future of imperfective verbs is usually formed with být in the future + infinitive.

So:

• bude mít = he will have
• nebude mít = he will not have

This is different from perfective verbs like přijít, where the present form already has future meaning:

• přijdu = I will come

So in one sentence you get both patterns:

• přijdu = future of a perfective verb
• nebude mít = future of an imperfective verb

Because mít takes a direct object, and the direct object goes in the accusative case.

The base noun is:

• dobrá nálada = a good mood

But after mít, it changes to accusative:

• mít dobrou náladu = to have a good mood / to be in a good mood

Both words change as needed:

• dobrá → dobrou
• nálada → náladu

This is a very useful expression to remember as a whole:

• mít dobrou náladu = to be in a good mood
• mít špatnou náladu = to be in a bad mood

Yes.

The sentence has two clauses:

1. Jestli přijdu do kanceláře pozdě = subordinate clause
2. šéf nebude mít dobrou náladu = main clause

In the main clause:

• šéf = subject
• nebude mít = verb
• dobrou náladu = object

So the boss is the one who won’t have a good mood.

Yes.

In Czech, a subordinate clause introduced by a word like jestli is normally separated by a comma from the main clause.

So:

• Jestli přijdu do kanceláře pozdě, šéf nebude mít dobrou náladu.

That comma is standard and expected.

Yes.

You can also say:

• Šéf nebude mít dobrou náladu, jestli přijdu do kanceláře pozdě.

The meaning stays basically the same.

Czech word order is more flexible than English, but the version with the conditional clause first is very natural and common.

It can suggest either, depending on context.

The verb přijít often has the sense of arrive / come as a completed movement. So:

• přijdu do kanceláře can be understood as I come to the office or I arrive at the office

In this sentence, English would often naturally say:

• If I get to the office late...
• If I come to the office late...
• If I arrive at the office late...

All are close in meaning.

Then Czech would usually use the conditional form:

• Kdybych přišel do kanceláře pozdě, šéf by neměl dobrou náladu.

That is more like:

• If I came / were to come to the office late, the boss wouldn’t be in a good mood.

So the difference is roughly:

• Jestli přijdu... = if I come / if I do come
• Kdybych přišel... = if I came / if I were to come

This is an important distinction in Czech.