Δεν κοιμάμαι καλά όταν έχει θόρυβο στη γειτονιά.

I don’t sleep well when there is noise in the neighborhood.

Breakdown of Δεν κοιμάμαι καλά όταν έχει θόρυβο στη γειτονιά.

• καλά: well
• δεν: not
• σε: in
• όταν: when

Questions & Answers about Δεν κοιμάμαι καλά όταν έχει θόρυβο στη γειτονιά.

Why does the sentence start with Δεν and where does it go in Greek?

Δεν is the standard negation for the indicative mood (statements/facts) in Modern Greek. It normally comes right before the verb it negates: Δεν κοιμάμαι = I don’t sleep / I’m not sleeping.
If there are other elements (like object pronouns), Δεν still stays immediately before the verb (e.g., Δεν το ξέρω).

What form is κοιμάμαι? Is it present tense?

Yes. κοιμάμαι is 1st person singular, present tense, middle/passive-form verb meaning I sleep / I’m sleeping.
Greek often uses the present for general/habitual statements, so here it naturally means something like I don’t sleep well (in general) when….

Why isn’t εγώ (I) included?

Greek is a pro-drop language: the subject pronoun is usually omitted because the verb ending shows the person/number.
You can add εγώ (Εγώ δεν κοιμάμαι καλά…) for emphasis/contrast (e.g., I don’t sleep well, but others do).

What exactly does καλά mean here, and why is it καλά and not an adjective?