Learn Hardcore Russian: Темнота в коридоре мешает мне найти выход. - The darkness in the corridor prevents me from finding the exit.

Темнота means darkness as a thing/phenomenon and can be the grammatical subject of a sentence: Темнота … мешает = The darkness … prevents/hinders.
Темно means it’s dark (a state) and is used in impersonal sentences, e.g. В коридоре темно. = It’s dark in the corridor.
Both are natural, but they build different sentence types.

What case is в коридоре, and why?

В коридоре is prepositional case (locative meaning) because в + prepositional typically answers where? (где?) when talking about location:

в коридоре = in the corridor (location)
If it were motion “into,” you’d usually get в + accusative: в коридор (direction).

Why is it мешает мне—what case is мне, and what does мешать govern?

Мне is dative case. The verb мешать commonly follows the pattern:

X мешает Y-дат. + infinitive
Meaning: X interferes with Y doing something / prevents Y from doing something.
So Темнота мешает мне… literally: Darkness hinders (to) me…

Is the word order fixed? Could мне go somewhere else?

Russian word order is flexible. The neutral version here is common:

Темнота в коридоре мешает мне найти выход.
But you can move мне for emphasis or rhythm:
Темнота в коридоре мне мешает найти выход. (emphasis: it’s me who’s affected)
Мне мешает темнота в коридоре найти выход. (topic = to me, the darkness…)
The meaning stays basically the same; nuance changes.

Why is найти used (perfective) instead of находить (imperfective)?

Найти is perfective and focuses on reaching a result: to find (successfully).
Here the idea is “I can’t manage to find the exit (reach the result).”
Находить (imperfective) would lean toward a repeated/habitual process or general ability, e.g.:

Темнота мешает мне находить выход. = darkness makes it hard for me to find the exit (in general / repeatedly).

What case is выход, and why isn’t there a preposition like к or из?

Выход is accusative, because найти takes a direct object: найти что? = to find what?
No extra preposition is needed because the meaning is “find the exit (as an object).”
If you wanted “a way out” or direction “out of,” you’d restructure, e.g. найти выход из здания (the exit out of the building).

Does мешает mean “prevents” or just “makes it difficult”? How strong is it?

Мешает sits between annoys/gets in the way and hinders/prevents. It often implies interference that makes something hard, not necessarily impossible.
If you want a stronger “doesn’t allow,” Russian often uses:

не даёт мне найти выход = doesn’t let me find the exit

Why is мешает singular? What is the subject?

The subject is Темнота (singular feminine noun), so the verb is мешает (3rd person singular).
The phrase в коридоре just describes where the darkness is; it doesn’t affect agreement.

How would you negate this sentence correctly?

You typically negate the verb:

Темнота в коридоре не мешает мне найти выход. = The darkness in the corridor doesn’t hinder me from finding the exit.
You can also negate the infinitive idea (less common here):
… мешает мне не найти выход would sound odd because it suggests “hinders me from not finding,” i.e. pushes me toward finding it.

How is this sentence pronounced / where is the stress?

Common stresses: темнотá, коридóре, мешáет, найтí, выхóд.
A rough transliteration with stress marks: Temnotá v koridóre mesháet mne naytí vykhód.
Also note в often sounds like [v] and can blend with the next word: вкоридóре in fast speech.