Из-за спешки я чуть не сел не на тот троллейбус.

Из-за means because of / due to, and it requires the genitive case.

• спешка = haste, rush
• genitive singular: спешки

So:

• из-за спешки = because of the rush / because I was in a hurry

A useful pattern:

• из-за дождя = because of the rain
• из-за работы = because of work
• из-за спешки = because of haste

Also, из-за often sounds a bit like the cause led to a problem or unwanted result, which fits this sentence well.

Чуть не + past tense verb means almost — specifically, almost did something, but in fact did not.

So:

• я чуть не сел... = I almost got on / I nearly got on...

Examples:

• Я чуть не упал. = I almost fell.
• Он чуть не забыл. = He almost forgot.

So in your sentence, the speaker is saying that he did not actually get on the wrong trolleybus, but came very close to doing so.

Because they belong to different parts of the sentence.

1. чуть не сел = almost got on
2. не на тот троллейбус = not the right trolleybus / the wrong trolleybus

So the structure is:

• чуть не = almost
• не на тот = not the one intended

They do not cancel each other out.

A natural way to understand the whole sentence is:

• Because I was in a hurry, I almost got on the wrong trolleybus.

Сел is the perfective past of сесть and focuses on a single completed action: getting on / sitting down.

Here the speaker is talking about one near-event:

• he almost got on the wrong trolleybus

That is why сел is more natural.

Compare:

• садиться = imperfective, process / repeated / general
• сесть = perfective, one completed act

Examples:

• Я садился в автобус, когда... = I was getting on the bus when...
• Я сел в автобус. = I got on the bus.

In this sentence, чуть не сел means he almost completed that one action.

Literally, yes, сесть means to sit down. But with transport, it often means to get on / board / take.

So:

• сесть на троллейбус = to get on / board a trolleybus

This is very common in Russian. The literal image is less important than the idiomatic meaning in context.

Similar examples:

• сесть на автобус = get on a bus
• сесть на поезд = get on a train
• сесть на трамвай = get on a tram

So in this sentence, you should understand сел as got on / boarded, not just physically sat down.

With transport, Russian often uses сесть на in the sense of board / take a vehicle.

So:

• сесть на автобус
• сесть на поезд
• сесть на троллейбус

This is idiomatic and very common.

You may also see в with some vehicles in other contexts, especially when emphasizing being physically inside:

• войти в автобус = enter the bus
• сесть в машину = get into the car

But with public transport, сесть на is extremely standard when talking about boarding it as a means of travel.

Не на тот means not the right one or the wrong one.

The key word is тот, which means that one. In context, it refers to the trolleybus the speaker was supposed to take.

So:

• на тот троллейбус = on the right / intended trolleybus
• не на тот троллейбус = on the wrong trolleybus

This is a very common Russian pattern:

• Я пришёл не в тот дом. = I came to the wrong house.
• Она села не в тот поезд. = She got on the wrong train.
• Мы повернули не на ту улицу. = We turned onto the wrong street.

Because троллейбус is a masculine inanimate noun, and for those nouns, the accusative singular is the same as the nominative singular.

So:

• nominative: троллейбус
• accusative: троллейбус

It is accusative here because сесть на что? takes the accusative:

• на троллейбус
• на автобус
• на поезд

Compare with a feminine noun:

• на маршрутку — here you can clearly see the accusative ending -у

Yes, Russian word order is flexible, but this version sounds natural and clear.

Current order:

• Из-за спешки = because I was in a hurry
• я = I
• чуть не сел = almost got on
• не на тот троллейбус = the wrong trolleybus

This puts the basic action first and the mistake after it.

Other possible variants include:

• Из-за спешки я чуть не на тот троллейбус сел.
• Я из-за спешки чуть не сел не на тот троллейбус.

These can be grammatical, but the original sounds more neutral and natural for most situations.

Yes. The past tense verb would agree with the speaker’s gender.

• male speaker: я чуть не сел
• female speaker: я чуть не села

So a woman would say:

• Из-за спешки я чуть не села не на тот троллейбус.

This is a very common feature of Russian past tense verbs.

They are related, but they are different parts of speech.

• спешить = to hurry, to be in a hurry
• спешка = haste, rush

So:

• Я спешил. = I was in a hurry.
• Из-за спешки... = Because of haste...

A more verbal way to say something similar would be:

• Поскольку я спешил, я чуть не сел не на тот троллейбус.

But the original sentence with из-за спешки is concise and natural.

Yes — that is the most natural English translation.

More literal versions might be:

• Because of being in a hurry, I almost got on not the right trolleybus.
• Due to the rush, I nearly boarded the wrong trolleybus.

But the best normal English version is:

• Because I was in a hurry, I almost got on the wrong trolleybus.

Yes. Из-за is the normal choice here for because of when talking about a reason or cause, especially one that led to a problem.

• из-за спешки = because of haste

Using из-за suggests that the haste caused the near-mistake.

Compare:

• от спешки is much less natural here
• из спешки would be incorrect

So for this sentence, из-за is exactly what you would expect a native speaker to use.