W formularzu było dziewiętnaście pytań, dlatego wypełniałam go długo.

Polish often drops subject pronouns when they are already clear from the verb form.

Here, wypełniałam already tells you:

• 1st person singular = I
• feminine speaker = a woman is speaking

So ja is unnecessary. If you added ja, it would usually add emphasis or contrast, for example Ja wypełniałam go długo, nie ty.

Because w here means in and requires the locative case.

• dictionary form: formularz
• after w: w formularzu

Polish usually says w formularzu for something contained within a form, even though English often says on the form.

So:

• W formularzu było dziewiętnaście pytań = there were nineteen questions in/on the form
• Na formularzu would sound more like on the physical surface of the form

This is a very common difficulty for learners.

With numeral phrases from 5 upward used as the subject, Polish normally uses the verb in 3rd person singular neuter in the past tense.

So:

• Było dziewiętnaście pytań = correct
• Były dziewiętnaście pytań = incorrect

Even though the meaning is plural, the grammar with 5+ numerals works differently from English.

After dziewiętnaście and other numerals from 5 upward, the noun goes into the genitive plural.

The noun is:

• singular: pytanie
• genitive plural: pytań

So:

• dziewiętnaście pytań
• pięć pytań
• jedenaście pytań

This is the normal pattern after 5, 6, 7... 19... and so on.

Those numbers behave differently.

• jedno pytanie było
• dwa pytania były
• trzy pytania były
• cztery pytania były

So:

• 1 takes the singular noun
• 2–4 usually take a nominative plural form like pytania
• 5+ usually take genitive plural, like pytań, and the verb becomes było

A useful contrast is:

• Były trzy pytania
• Było pięć pytań

Also remember that the teen numbers are exceptions:

• dwadzieścia dwa pytania
• but dwanaście pytań

This is about aspect.

• wypełniać = imperfective
• wypełnić = perfective

In this sentence, wypełniałam is used because the speaker is focusing on the process/duration of filling in the form, which matches długo.

So:

• wypełniałam go długo = I was filling it in for a long time / it took me a long time to fill it in
• wypełniłam go = I filled it in / I completed it

The imperfective is more natural when the important idea is how long the activity lasted.

Yes.

In the past tense, Polish verbs agree with the speaker’s gender in the singular.

• wypełniałam = I (female) was filling in / filled in
• wypełniałem = I (male) was filling in / filled in

So this sentence can only be said by a female speaker as written.

Not necessarily.

The imperfective wypełniałam does not clearly state whether the action was completed. It focuses on the activity as a process.

So the sentence tells you:

• the action took a long time

But it does not explicitly guarantee:

• that the form was finished

If you wanted to make completion clear, you could say:

• W końcu go wypełniłam
• Wypełniłam go po długim czasie

Go means it here, referring to formularz.

The verb wypełniać takes a direct object, and here that object is the form. Instead of repeating formularz, Polish uses the object pronoun go.

So:

• wypełniałam formularz = I was filling in the form
• wypełniałam go = I was filling it in

This is natural because formularz is masculine singular.

No. Here długo means for a long time.

That is about duration, not speed.

Compare:

• wypełniałam go długo = I was filling it in for a long time
• wypełniałam go wolno = I was filling it in slowly

So the sentence means that the form took a long time because it had many questions, not necessarily that the person worked slowly.

Dlatego means something like:

• therefore
• that is why
• so

It introduces the result of the first clause:

• there were nineteen questions
• therefore / that is why it took a long time to fill in

The comma is used because Polish is separating two clauses:

• W formularzu było dziewiętnaście pytań, dlatego...

This punctuation is normal here.

Polish word order is fairly flexible, but the version in the sentence is very natural.

This order works well because:

• W formularzu sets the scene first
• dlatego introduces the consequence
• go stays close to the verb

You could rearrange parts of the sentence, but the emphasis would change. For example:

• Było dziewiętnaście pytań w formularzu, dlatego długo go wypełniałam.

This is understandable, but the original sounds smoother and more natural.

So the word order is not absolutely fixed, but it is chosen for natural flow and emphasis.