Powinnam była wziąć większy koszyk, bo ten był za mały.

Powinnam była wziąć expresses “I should have taken” — a regret about a past action.

• powinnam = I should
• była helps push the meaning into the past
• wziąć = to take

So the full pattern means something like: I was supposed to have taken / I should have taken.

In everyday Polish, people very often shorten this and simply say:

• Powinnam wziąć większy koszyk.

This can also mean I should have taken a bigger basket, depending on context. But powinnam była wziąć is more explicitly past-looking.

Yes. The forms powinnam and była are both feminine singular.

A male speaker would say:

• Powinienem był wziąć większy koszyk, bo ten był za mały.

So this sentence specifically sounds like it is spoken by a woman.

This is part of a common Polish structure used for past obligation/regret.

• powinnam already agrees with the speaker in gender and number
• była is the feminine past form of być (to be)

Together they form a kind of past-looking expression: powinnam była wziąć.

It may feel redundant to an English speaker, but it is a normal Polish pattern. Compare:

• powinnam była zrobić = I should have done
• powinienem był zrobić = I should have done (male speaker)

Because wziąć is perfective, and here we are talking about one completed action: taking a basket.

• brać = to be taking / to take in an ongoing, repeated, or uncompleted sense
• wziąć = to take once, as a complete action

Since the meaning is “I should have taken a bigger basket”, Polish prefers wziąć.

If you used brać, it would sound wrong or at least unnatural in this context.

It is in the accusative, because it is the direct object of wziąć (to take).

You take what?
→ większy koszyk

So logically it is accusative.

However, for a masculine inanimate noun like koszyk, the accusative singular looks the same as the nominative:

• nominative: większy koszyk
• accusative: większy koszyk

That is why it looks unchanged.

Because koszyk is:

• masculine
• singular
• inanimate

And in the accusative singular, masculine inanimate adjectives usually have the same form as in the nominative.

So:

• większy koszyk = a bigger basket

If the noun were feminine, the form would change, for example:

• większą torbę = a bigger bag

Here ten means “this one”.

The full idea is:

• bo ten był za mały = because this one was too small

The noun koszyk is omitted because it is already understood from the earlier part of the sentence. In fuller form, you could say:

• bo ten koszyk był za mały

But Polish often leaves the noun out when it is obvious.

Because the speaker is referring to the situation in the past.

The basket they took was too small at that time, so Polish uses the past tense:

• był = was

If you said jest za mały, that would mean it is too small now, focusing on the present.

Za mały means too small.

This is a very common Polish pattern:

• za
  • adjective = too ...

Examples:

• za drogi = too expensive
• za duży = too big
• za ciężki = too heavy

So:

• ten był za mały = this one was too small

Yes, Polish word order is fairly flexible, but the given sentence is the most natural neutral version:

• Powinnam była wziąć większy koszyk, bo ten był za mały.

You could also say:

• Bo ten był za mały, powinnam była wziąć większy koszyk.

That puts more emphasis on the reason first: Because this one was too small...

But not every rearrangement sounds equally natural. The original sentence is a very standard way to say it.

No. Bo is very common and natural in everyday speech. It means because.

You could also use:

• ponieważ = because / since
• gdyż = because (more formal/bookish)

So you could say:

• Powinnam była wziąć większy koszyk, ponieważ ten był za mały.

That is correct, but bo sounds more conversational and fits this sentence very well.

Yes, you could, and it would still be understandable in context.

But ten helps make the meaning clearer:

• bo ten był za mały = because this one was too small

Without ten, the sentence is a bit less explicit about what was too small. Since the speaker is contrasting the basket they took with the bigger basket they should have taken, ten works very naturally here.

In this context, it expresses regret about a past choice.

Literally, powinnam relates to obligation or what would have been the right thing to do, but in real use:

• Powinnam była wziąć większy koszyk
  usually means
• I should have taken a bigger basket

So it sounds like the speaker now realizes their earlier decision was wrong.