Η ακαταστασία στο δωμάτιό μου είναι τόσο μεγάλη που δεν βρίσκω τα κλειδιά μου.

Greek uses the definite article much more often than English.

• Η ακαταστασία = the mess / the untidiness
• In English, we might simply say Mess in my room is so bad..., but Greek normally prefers the article here.

Also, ακαταστασία is a feminine singular noun, so the article is η.

In Greek, every noun has a grammatical gender: masculine, feminine, or neuter.
Ακαταστασία is feminine, so words connected to it must agree with it.

That is why you get:

• η ακαταστασία — feminine article
• μεγάλη — feminine form of big/great

So the grammar is based on the noun’s gender, not on any real-world idea of femininity.

στο is a contraction of:

• σε = in / to / at
• το = the

So:

• στο δωμάτιό μου = in my room

Literally, it is:

• σε το δωμάτιό μου → στο δωμάτιό μου

This contraction is extremely common in Greek.

In Greek, possessive forms like μου, σου, του, της usually come after the noun.

So:

• το δωμάτιό μου = my room
• τα κλειδιά μου = my keys

This is one of the most basic Greek possessive patterns.

English: my room
Greek: the room my

That may feel backward to an English speaker, but it is completely normal in Greek.

This is a common feature of Greek pronunciation and spelling.

The noun by itself is:

• δωμάτιο

When an unstressed possessive like μου follows, Greek often adds or preserves an extra accent to show the correct stress pattern:

• το δωμάτιό μου

This helps keep the pronunciation clear. You do not need to think of it as a different word—just the same noun in a common accented pattern before μου.

τόσο means so or so much in this sentence.

The pattern is:

• τόσο + adjective + που
  = so + adjective + that

So:

• είναι τόσο μεγάλη που...
  = it is so great/big that...

Here, τόσο modifies the adjective μεγάλη.

A very literal breakdown is:

• είναι = is
• τόσο μεγάλη = so great / so big
• που = that

Because μεγάλη must agree with ακαταστασία, which is feminine singular.

The adjective μεγάλος changes form:

• μεγάλος — masculine
• μεγάλη — feminine
• μεγάλο — neuter

Since the noun is feminine:

• η ακαταστασία είναι μεγάλη

This kind of agreement is one of the most important parts of Greek grammar.

Yes—here που means that in the structure so ... that.

The sentence uses a result clause:

• τόσο μεγάλη που δεν βρίσκω τα κλειδιά μου
• so great that I can’t find my keys

This is a very common Greek pattern:

• τόσο... που... = so... that...

So που is linking the result to the first part of the sentence.

βρίσκω is the present/imperfective form, and here it means I can’t find or I am not finding.

Greek often uses the present tense for a current ongoing situation:

• δεν βρίσκω τα κλειδιά μου = I can’t find my keys

This sounds natural if the speaker is currently looking and failing to find them.

An aorist-based form would usually point more to a single completed event, which is not the main idea here. The present fits the idea of an ongoing problem caused by the mess.

Because κλειδιά is:

• neuter plural
• the plural of κλειδί = key

So the article must also be neuter plural:

• το κλειδί = the key
• τα κλειδιά = the keys

Then you add the possessive:

• τα κλειδιά μου = my keys

So the full object is:

• δεν βρίσκω τα κλειδιά μου
  = I can’t find my keys

Greek word order is more flexible than English word order, because the endings often show what each word is doing.

This sentence is very natural as written:

• Η ακαταστασία στο δωμάτιό μου είναι τόσο μεγάλη που δεν βρίσκω τα κλειδιά μου.

But Greek could move parts around for emphasis. For example, a speaker might shift στο δωμάτιό μου or stress τα κλειδιά μου in speech.

Even so, the original order is a very good, standard way to say it.

Yes, that would also be possible, but it expresses the idea a bit differently.

Your original sentence says:

• The mess in my room is so great that I can’t find my keys.

This emphasizes the degree of the mess by using:

• τόσο... που... = so... that...

The alternative with επειδή would mean:

• I can’t find my keys because my room is messy.

That version gives a plain reason.
The original is stronger and more expressive because it highlights how bad the mess is.