Mieliśmy wyjść wcześniej na wyprzedaż, ale córka miała jeszcze oddać książki do biblioteki.

Here mieliśmy is not the usual we had / we possessed meaning of mieć.

The pattern mieć + infinitive often means:

• to be supposed to
• to have to
• to be expected to
• sometimes to have planned to

So Mieliśmy wyjść wcześniej means something like:

• We were supposed to leave earlier
• We had planned to leave earlier
• We were meant to go out earlier

The exact English translation depends on context, but the idea is that there was an intention, plan, or obligation.

Because the sentence talks about two different subjects:

• mieliśmy wyjść = we were supposed to leave
• córka miała oddać = the daughter was supposed to return

So each subject gets its own past-tense form of mieć:

• my → mieliśmy
• córka → miała

This is very natural in Polish when describing planned or expected actions in the past.

Wyjść is the perfective form, while wychodzić is imperfective.

Here wyjść is used because the sentence refers to a single completed action:

• to leave / to go out at a particular moment

So mieliśmy wyjść wcześniej means we were supposed to leave earlier as one completed event.

If you used wychodzić, it would suggest repeated action or focus on the process, which does not fit as well here.

For the same reason as wyjść: oddać is perfective.

• oddać = to return / hand back once, successfully, as a completed action
• oddawać = to be returning / to return repeatedly / to return in general

In a library context, oddać książki do biblioteki means to return the books to the library as a completed task. That is why the perfective verb fits well.

It means the daughter still had to return the books to the library or was still supposed to return the books to the library.

The word jeszcze is important here. It adds the idea that this task was still remaining or had not been done yet.

So the sentence suggests:

• we were supposed to leave earlier,
• but that could not happen yet,
• because the daughter still needed to return the books.

Here jeszcze means still or yet.

In córka miała jeszcze oddać książki, it suggests an unfinished obligation:

• she still had to return the books
• she had yet to return the books

It does not mean more here. It points to something that remained to be done before something else could happen.

In Polish, iść / wyjść na + event/activity is very common.

So:

• na wyprzedaż = to the sale
• literally something like out to a sale / for the sale event

This is similar to patterns like:

• iść na koncert = to go to a concert
• iść na zakupy = to go shopping
• iść na imprezę = to go to a party

So na wyprzedaż is idiomatic because a sale is treated like an event or occasion.

Because na here takes the accusative case, and wyprzedaż is a feminine noun whose accusative singular looks the same as the nominative singular.

So:

• nominative: wyprzedaż
• accusative: wyprzedaż

There is a case change grammatically, but the form does not change in spelling.

Because do requires the genitive case.

The base form is:

• biblioteka = library

After do, it becomes:

• do biblioteki = to the library

This is a very common pattern:

• do domu = to the house / home
• do szkoły = to school
• do sklepu = to the shop

So oddać książki do biblioteki means to return the books to the library.

Here książki is accusative plural because it is the direct object of oddać.

The noun is:

• singular: książka = book
• plural nominative: książki
• plural accusative: książki

For many non-masculine-personal plural nouns, the nominative and accusative forms are the same. So although książki looks like nominative plural, here it is functioning as accusative plural.

Wcześniej means earlier.

So:

• Mieliśmy wyjść wcześniej = We were supposed to leave earlier

It compares the expected time of leaving with some later time that either actually happened or was being discussed.

Polish often allows subject pronouns to be omitted because the verb ending already shows who the subject is.

For example:

• mieliśmy already tells you the subject is we
• miała already tells you the subject is she

That is why Polish does not need my or ona here.

English usually does need the subject:

• We were supposed to leave earlier...
• ...but the daughter still had to return the books...

So this is a normal example of Polish being more flexible about dropping pronouns.

No, Polish word order is fairly flexible, but this version sounds natural and clear.

The sentence:

• Mieliśmy wyjść wcześniej na wyprzedaż, ale córka miała jeszcze oddać książki do biblioteki.

puts the main plan first, then the reason for the delay.

The order also helps highlight:

1. the intended action: we were supposed to leave earlier
2. the contrast: ale
3. the unfinished task: córka miała jeszcze oddać książki

You could move some elements around, but this order is very natural in ordinary speech and writing.

Here ale simply introduces a contrast:

• we were supposed to leave earlier,
• but something prevented or delayed that.

So ale connects the two ideas in a very straightforward way. It shows that the daughter’s unfinished task explains why the earlier departure did not happen as planned.