В тот же день я оставила вторую заявку, потому что в коридоре не работала розетка и нужен был электрик.

Because в + a time expression like день usually takes the accusative to mean on/that day.

• тот → accusative masculine = тот (same form as nominative)
• же is an emphasizing particle meaning the very / same
  So В тот же день = On that same day / That very day.

же adds emphasis: тот же день = the same day (as previously mentioned) / that very day.
You can omit it, but the meaning becomes less “same-as-before” and more neutral:

• В тот день = On that day
• В тот же день = On that same day

Russian past tense agrees with the subject in gender and number.

• Female speaker: я оставила
• Male speaker: я оставил
• Plural: мы оставили

In this context оставить заявку is a common collocation meaning to submit / to leave a service request. It’s like “leave a request with the office/system.”
Other verbs exist but can sound different:

• подать заявку = to file/submit an application/request (more official/formal)
• сделать заявку is possible but less standard than оставить/подать for this noun.

It’s the accusative object of the verb оставила (left/submitted what?).
заявка is feminine, so вторая (nominative) becomes вторую (accusative feminine).

Common distinctions:

• заявка = a request/order/application in a practical system (service request, booking request, job application in some contexts)
• запрос = an inquiry/request for information, or a “request” in a more abstract/official sense (also “query”)
• заявление = a written statement/application, often formal (e.g., to an institution), or “statement” as a declaration

Here it’s likely a building/maintenance service request, so заявка fits best.

Because потому что introduces a subordinate clause (a “because” clause). In Russian, that clause is normally separated by a comma: ..., потому что ...

Yes. Both are common:

• Я оставила вторую заявку, потому что ... (reason after the main action)
• Потому что ..., я оставила вторую заявку. (reason first; more emphatic/less neutral)

With в:

• в + accusative (в коридор) = motion into (going into the corridor)
• в + prepositional (в коридоре) = location in (already there)

Here it’s about where the outlet is located, so в коридоре.

Yes, that’s a very natural way to say an electrical socket/outlet wasn’t functioning.
работать is widely used for devices/systems: the elevator works, the internet works, the outlet works, etc.

не работала describes an ongoing state/condition: the outlet was not functioning (at that time). Imperfective is typical for states and repeated/ongoing situations. Perfective would sound like a single completed event, which doesn’t fit as well here.

This is a common Russian structure: нужен/нужна/нужно/нужны (short adjective meaning “needed”) + optional быть in past/future.

• Present: нужен электрик = an electrician is needed
• Past: нужен был электрик = an electrician was needed
• Future: нужен будет электрик = an electrician will be needed

In the past, был is usually included.

Because нужен agrees with the thing that is needed: электрик is masculine.
If it were помощь (feminine), you’d get: нужна была помощь.

In нужен был электрик, электрик is the grammatical subject of an impersonal-style statement meaning “An electrician was needed.” So it stays nominative.

Both are correct; they differ slightly:

• нужен был электрик = general/impersonal: an electrician was needed (for the situation)
• мне нужен был электрик = explicit personal need: I needed an electrician

Russian often omits мне when the context already makes it clear.

It connects two reasons inside the “because” part: 1) в коридоре не работала розетка
2) (и) нужен был электрик
So the speaker submitted a second request because the outlet didn’t work, and an electrician was needed.