В маршрутке я делаю голосовую запись на телефон, чтобы не забыть новые слова.

Маршрутке is in the prepositional case (also called locative), singular feminine, from маршрутка.

With the preposition в, Russian uses:

• в + prepositional to mean “in / inside something” (location, no movement):

  • в маршрутке – in the minibus
  • в школе – at school
  • в автобусе – on / in the bus

• в + accusative to mean “into / to (movement)”:

  • в маршрутку – into the minibus
  • в школу – to school

In this sentence there is no movement; it describes where the person is, so we use в маршрутке with the prepositional case.

A маршрутка is a small minibus or shared taxi that runs on a fixed route and usually has a number, like a bus line. It’s common in Russia and other post‑Soviet countries.

Possible translations:

• minibus (on a fixed route)
• shared taxi
• Sometimes just bus, if you don’t need the extra nuance

But маршрутка is normally smaller and more informal than a regular public автобус (bus).

Делаю голосовую запись literally means “I make a voice recording” and sounds normal and neutral.

Other options:

• делаю аудиозапись – I make an audio recording
• записываю голосовое сообщение – I’m recording a voice message (e.g. in a messenger app)
• записываю новые слова на телефон – I’m recording the new words on my phone

Записываю голос (“I record voice”) is understandable but a bit vague and not idiomatic on its own; you’d usually specify голосовое сообщение, голос кого‑то, etc.

So делаю голосовую запись is a very natural, clear choice here.

На телефон literally means “onto the phone” and is the usual way to say you are saving / recording something on a device:

• записать номер на телефон – save a number on the phone
• скачать фильм на компьютер – download a movie onto the computer
• скинуть файлы на флешку – put the files onto the flash drive

Russian often uses на (“onto”) with:

• devices: на телефон, на компьютер, на диск, на флешку
• surfaces / media: на бумаге (on paper), на доске (on the board)

В телефон would sound like “into the physical interior of the phone” and is not how people talk about recordings or files. So на телефон is the natural choice.

Чтобы introduces a purpose clause: “in order to / so that”.

There are two main patterns:

1. Чтобы + infinitive (same subject)
   Used when the subject of both verbs is the same (here: “I”):

   • делаю запись, чтобы не забыть – I make a recording in order not to forget.

   This is exactly our sentence: я делаю …, чтобы не забыть.

2. Чтобы + past tense (usually with a pronoun/noun)
   More explicit, often when the subject changes:

   • Я записываю, чтобы ты не забыл. – I record it so that you don’t forget.
   • Я делаю запись, чтобы я не забыл. – I make a recording so that I don’t forget.

In our sentence we can say чтобы я не забыл, but it sounds heavier and a bit more formal.
Чтобы не забыть is shorter and very natural when the “I” is obvious from the main clause.

This is about aspect:

• забыть – perfective: “to forget (as a single completed event)”
• забывать – imperfective: “to be forgetting / to forget regularly / to tend to forget”

In a purpose clause with чтобы, if the goal is to avoid one particular act of forgetting, Russian usually uses the perfective:

• делаю запись, чтобы не забыть – I make a recording so that I won’t (end up) forget(ing) (this once).

If you said чтобы не забывать, it would suggest preventing repeated or habitual forgetting (“so that I don’t keep forgetting”), which is a bit different. For one set of new words learned now, не забыть is the natural choice.

• голосовую запись

  • Base form (nominative): голосовая запись – voice recording
  • In the sentence: голосовую запись – accusative singular feminine
  • The adjective голосовую agrees with запись in gender (fem.), number (sg.), and case (accusative).

• новые слова

  • Base form (nominative): новые слова – new words
  • In the sentence: also accusative plural.
    For inanimate nouns, nominative plural = accusative plural, so слова and новые look the same in both cases.

Both голосовую запись and новые слова are direct objects of their verbs (делаю, не забыть), so they are in the accusative case.

Yes. Russian word order is flexible, and several versions are grammatically correct:

• В маршрутке я делаю голосовую запись на телефон…
  Current version. Puts в маршрутке first to set the scene (“When I’m in the minibus…”).

• Я в маршрутке делаю голосовую запись на телефон…
  Starts with я, then adds в маршрутке as extra info about where I am. Also natural.

• Я делаю голосовую запись на телефон в маршрутке…
  All in one line; в маршрутке comes last and sounds like an afterthought: “on my phone, in the minibus”.

All are possible. The meaning doesn’t change much; you only slightly shift what you emphasize first (place vs subject vs action). The original version sounds very natural and conversational.

Yes, you can omit я:

• В маршрутке делаю голосовую запись на телефон, чтобы не забыть новые слова.

Russian often drops personal pronouns when the subject is clear from the verb ending:

• делаю – clearly 1st person singular (“I do / I’m doing”)

The version without я sounds a bit more informal or narrative, as if you’re describing your typical behavior:
“(When I’m) in the minibus, (I) make a voice recording on my phone…”

Both versions are correct; including я is slightly more explicit and neutral.