Kdybychom zapomněli koupit dort, moje babička by se jen usmála a řekla, že důležitější je být spolu.

Kdybychom means if we were to or if we did in a hypothetical sense.

It is built from:

• kdyby = if
• -chom = the conditional ending for we

So kdybychom zapomněli means if we forgot / if we were to forget.

This is the standard written form. In informal speech, you may also hear nonstandard forms like kdybysme, but learners should use kdybychom.

Not necessarily. This is a conditional, not a simple past statement.

Czech forms the conditional with:

• an l-participle form such as zapomněli, usmála, řekla
• plus a conditional marker like by or the ending inside kdybychom

So although the verbs look similar to past tense forms, here they express a hypothetical situation:

• Kdybychom zapomněli koupit dort... = If we forgot / were to forget to buy a cake...
• babička by se usmála... = grandma would smile...

One extra detail: zapomněli is the form used for a mixed group or when the gender of we is not specified. If the group were all female, it could be zapomněly.

Because Czech normally marks the conditional in the main clause too.

So the pattern is:

• kdybychom zapomněli... = if we forgot / if we were to forget...
• babička by se usmála... = grandma would smile...

This is different from English, where learners are used to seeing would mainly in the result clause. In Czech, having a conditional form in both parts is completely normal.

Because the we part is already built into kdybychom.

Compare:

• simple past: Zapomněli jsme koupit dort. = We forgot to buy a cake.
• conditional if-clause: Kdybychom zapomněli koupit dort... = If we forgot / were to forget to buy a cake...

So you do not add jsme here, because the person and number are already expressed by -chom.

Because koupit is the perfective form, and here it refers to one complete action: buying the cake as a single event.

• koupit = to buy, to complete the purchase
• kupovat = to be buying, to buy repeatedly, or to focus on the process

After zapomenout + infinitive, Czech often uses the perfective verb when talking about forgetting to carry out one specific action:

• zapomněli koupit dort = we forgot to buy a cake

If you used kupovat, it would sound more process-oriented or less natural in this context.

Because koupit takes the accusative case, and dort is a masculine inanimate noun whose accusative singular looks the same as the nominative singular.

So:

• nominative: dort
• accusative: dort

That is why you see:

• koupit dort = to buy a cake

Not every noun stays the same in the accusative, but this one does.

Because the subject is moje babička, which is feminine singular.

In Czech, these participle forms agree with the subject in gender and number:

• babička usmála se
• babička řekla

If the subject were masculine, you would get:

• dědeček by se usmál a řekl

So the -a ending tells you the subject is feminine singular.

Here se is part of the verb usmát se, which means to smile.

It does not literally mean herself in this sentence. English says simply smile, but Czech uses a reflexive form:

• usmát se = to smile
• babička se usmála = grandma smiled

This is very common in Czech: some verbs require se even when English has no matching reflexive word.

Jen means only or just.

In this sentence:

• by se jen usmála a řekla...

it gives the sense would just smile and say...

Its position is natural because it modifies the action that follows. Czech word order is flexible, but this placement sounds very normal and clear.

Because že introduces a content clause, like English that.

So:

• řekla, že... = she said that...

In English, that is often omitted:

• She said that...
• She said...

In Czech, že is usually kept, so řekla, že... is the normal pattern.

Literally, it is something like:

• that more important is to be together

But natural English is:

• that being together is more important
• or that it is more important to be together

A few things are happening here:

1. důležitější is the comparative of důležitý

   • důležitý = important
   • důležitější = more important

2. Czech can use an infinitive phrase as the thing being talked about

   • být spolu = to be together

3. The word order puts emphasis on důležitější

   • že důležitější je být spolu
   • this highlights more important

You could also say:

• že je důležitější být spolu

That is also correct. The original version sounds a bit more stylistically shaped or emphatic.

Because Czech can leave the comparison understood from the context.

Here, the idea is:

• more important than the cake
• or more important than remembering the cake

But Czech does not need to say that part explicitly if it is obvious.

So:

• že důležitější je být spolu

naturally means something like:

• that what matters more is being together
• that being together is more important

If you wanted to state the comparison fully, you could add it, but it is not necessary here.