В поисковой строке я написала название фильма и быстро нашла его.

Because Russian past tense singular forms show gender.

• я написал = I wrote / I typed said by a man
• я написала = I wrote / I typed said by a woman

So this sentence tells you the speaker is female.

It is the prepositional case after в when в means in as a location.

The dictionary form is:

• поисковая строка = search bar / search field

In the prepositional singular, it becomes:

• в поисковой строке = in the search bar

Both words change because the adjective must agree with the noun:

• поисковая → поисковой
• строка → строке

So the phrase literally means in the search bar.

Because Russian often uses the genitive case for the pattern the X of Y.

Here:

• название = title / name
• фильм = film
• фильма = genitive singular of фильм

So:

• название фильма = the title of the film

This is a very common structure in Russian:

• цвет машины = the color of the car
• дверь дома = the door of the house
• начало фильма = the beginning of the film

Both verbs are perfective, which fits the idea of completed actions with a result.

• написала = she typed/wrote it and finished
• нашла = she found it successfully

The sentence describes a simple sequence of finished events:

1. She typed the film title.
2. She quickly found it.

If you used imperfective forms, the meaning would change:

• писала would sound more like was writing / was typing
• находила would usually mean used to find / kept finding, not one clear successful result

So perfective is the natural choice here.

Because искать means to look for, while найти means to find.

• искала = was looking for / looked for
• нашла = found

In this sentence, the result matters: she didn’t just search, she actually found the film. That is why Russian uses нашла.

It refers to the film: she quickly found it.

The key idea is:

• she typed the title of the film
• then she found the film itself

So его means it.

A small grammar note: его can mean him or it, depending on context. Here it clearly means it.

Yes, you may hear both, but the nuance is slightly different.

• в поисковой строке focuses on the location: in the search bar
• в поисковую строку focuses more on direction/target: into the search bar

With text entry, Russian often uses both kinds of wording depending on the verb and what the speaker wants to emphasize.

For example:

• Я ввела название фильма в поисковую строку.
  = I entered the film title into the search bar.

In your sentence, в поисковой строке is natural and emphasizes where the title was typed.

Russian word order is fairly flexible, and changing it often changes focus rather than basic meaning.

This sentence begins with В поисковой строке to set the scene first:

• In the search bar, I typed the film title...

A more neutral order is also possible:

• Я написала название фильма в поисковой строке и быстро нашла его.

That version is also natural. Starting with В поисковой строке just puts extra attention on where the action happened.

Because Russian has no articles like a and the.

So Russian says:

• в поисковой строке
• название фильма

and context tells you whether English should use a, the, or nothing.

That is completely normal in Russian. Learners have to get used to understanding definiteness from context instead of from articles.

Sometimes, yes.

Russian often omits subject pronouns when the subject is already clear from context. So in conversation, you might hear something like:

• В поисковой строке написала название фильма и быстро нашла его.

That can sound natural if it is already obvious that the speaker means I.

However, in the past tense, the verb does not show person, only gender/number, so я is often kept when you want to be fully clear. In your sentence, including я is completely normal and natural.