Когда я подошёл к двери, домофон снова зазвонил.

Подошёл is the masculine past-tense form of подойти, a perfective verb meaning to come up to / approach / walk up to.

Here it implies a completed movement: the speaker reached the door. It is not just was walking toward the door, but got to the door.

Compare:

• я подходил к двери = I was approaching the door / I used to approach the door
• я подошёл к двери = I approached the door / I came up to the door

Because this sentence describes one completed event in the past, подошёл is the natural choice.

The preposition к requires the dative case.

So:

• дверь = door (dictionary form, nominative)
• к двери = to the door / toward the door (dative)

This is a very common pattern:

• к дому = to the house
• к окну = to the window
• к человеку = to the person

So подойти к двери is the standard way to say approach the door.

Yes, двери can be either:

• singular dative/genitive/prepositional of дверь
• plural nominative/accusative of дверь

In this sentence, it is clearly singular dative because it follows к:

• к двери = to the door

Russian often has forms that look identical but are understood from context.

Домофон usually means an intercom, especially the door-entry system in an apartment building.

So in this sentence, it is not a regular phone inside the house. It is the device that rings when someone calls from the entrance.

That is why домофон снова зазвонил means the intercom rang again.

Зазвонил is a perfective verb meaning started ringing or, in many contexts, simply rang as a completed event.

Compare:

• звонил = was ringing / used to ring / rang repeatedly or as an ongoing process
• зазвонил = began to ring

In this sentence, the idea is that at that moment, the intercom rang again. Russian often uses за- with sounds to mark the beginning of the action:

• запел = started singing
• закричал = started shouting
• засмеялся = started laughing
• зазвонил = started ringing

Снова means again.

In Russian, adverbs like снова are fairly flexible in position, but домофон снова зазвонил is a very natural word order. It emphasizes that the ringing happened again.

Possible variants:

• домофон снова зазвонил
• снова зазвонил домофон
• домофон зазвонил снова

These can all work, but the first one is the most neutral here.

Because Когда я подошёл к двери is a subordinate clause introduced by когда (when).

Russian separates this kind of clause with a comma:

• Когда я подошёл к двери, домофон снова зазвонил.

This works like English:

• When I approached the door, the intercom rang again.

If the subordinate clause comes second, there is still a comma:

• Домофон снова зазвонил, когда я подошёл к двери.

Russian word order is more flexible than English, but this sentence uses a very standard, neutral order:

• Когда я подошёл к двери, домофон снова зазвонил.

The main clause begins with the subject домофон, then the adverb снова, then the verb зазвонил.

You could also say:

• Когда я подошёл к двери, снова зазвонил домофон.

That version sounds a bit more narrative or expressive, with slightly more focus on the event of ringing. But the original is the most straightforward.

Yes, Russian often drops personal pronouns when they are clear from the verb:

• Когда подошёл к двери, домофон снова зазвонил.

That can be possible in context, especially in informal speech or narrative.

But я is included here for clarity and naturalness. It makes the subject explicit: when I approached the door.

Russian does not omit pronouns as regularly as some other languages, but it does so much more often than English.

In the past tense, Russian verbs agree in gender and number with the subject.

Since the subject is я, the form depends on whether the speaker is male or female:

• я подошёл = said by a man
• я подошла = said by a woman

So this sentence, as written, suggests that the speaker is male.

Yes. Both снова and опять often mean again.

So you could say:

• домофон снова зазвонил
• домофон опять зазвонил

In many contexts they are very close. Very roughly:

• снова can sound a bit more neutral
• опять can sometimes sound more emotional, like again...

But this is only a tendency, not a strict rule. In this sentence, both are possible.

The main stresses are:

• когдá
• я
• подошёл
• к двéри
• домофóн
• снóва
• зазвони́л

A rough pronunciation guide:

• Когда = kag-DA
• я = ya
• подошёл = pa-da-SHOL
• к двери = g DVYE-ri
• домофон = da-ma-FON
• снова = SNO-va
• зазвонил = za-zva-NEEL

A natural rhythm is:

Когда́ я подошёл к две́ри, домофо́н сно́ва зазвони́л.

Yes, depending on context, English can translate когда here as either when or as.

But the Russian verb подошёл is perfective and completed, so the core idea is:

• when I got to / came up to / approached the door

If Russian wanted to emphasize the ongoing movement more strongly, it might use an imperfective form such as подходил in a different context. Since the sentence uses подошёл, the moment of arrival is important.