Im Flur ist die Glühbirne kaputt, deshalb bleibt die Jalousie heute offen.

im is the contraction of in dem.

Here it is used because:

• der Flur is masculine
• in with a location takes the dative
• so in dem Flur becomes im Flur

So:

• im Flur = in the hallway / in the corridor

If there were movement into the hallway, German would use the accusative instead:

• in den Flur = into the hallway

German main clauses follow the verb-second rule. That means the finite verb must be in the second position, but the first position can be many different things:

• the subject
• a time phrase
• a place phrase
• another adverbial element

Here, Im Flur is placed first to set the scene:

• Im Flur ist die Glühbirne kaputt.

Because Im Flur takes the first slot, the verb ist must come next, and the subject die Glühbirne comes after it.

Both patterns are possible in German, but they mean slightly different things in terms of emphasis.

• Die Glühbirne ist kaputt. → starts with the subject
• Im Flur ist die Glühbirne kaputt. → starts with the location

In German, once something other than the subject is put first, the verb still has to stay in second position. That is why you get:

• Im Flur
  • ist
    • die Glühbirne
      • kaputt

This is a very common feature of German word order.

Because kaputt is a predicate adjective here. After verbs like:

• sein = to be
• bleiben = to stay/remain
• werden = to become

German adjectives do not take adjective endings.

So:

• die Glühbirne ist kaputt
• die Jalousie bleibt offen

But before a noun, the adjective does take an ending:

• die kaputte Glühbirne
• die offene Jalousie

That is a very important contrast.

Glühbirne means light bulb.

It is feminine, so its basic dictionary form is:

• die Glühbirne

A useful extra point: German compound nouns usually take their gender from the last part of the word. The last part here is Birne, and die Birne is feminine, so the whole compound is feminine too:

• die Glühbirne

deshalb means therefore, that’s why, or for that reason.

It is not a subordinating conjunction like weil. Instead, it is an adverb that starts a new main clause. Because it takes the first position in that clause, the verb must come immediately after it:

• deshalb bleibt die Jalousie heute offen

Not:

• deshalb die Jalousie bleibt heute offen

So the pattern is:

• deshalb
  • verb
    • subject
      • ...

This is one of the most common learner questions about words like deshalb, dann, trotzdem, and daher.

bleiben means to stay or to remain.

So:

• Die Jalousie bleibt offen = The blind stays/remains open

This emphasizes that it continues to be open or is left open.

If you said:

• Die Jalousie ist offen

that would simply describe its state: The blind is open.

So bleibt adds the idea of continuation.

For the same reason as kaputt: it is a predicate adjective after bleiben.

So you say:

• die Jalousie bleibt offen

But before a noun:

• die offene Jalousie

No ending after bleiben, but an ending before a noun.

In German, die Jalousie usually means a blind or shutter, especially for a window.

It is a feminine noun:

• die Jalousie

Depending on context, English might translate it as:

• blind
• window blind
• shutter

In the second clause, heute is a time adverb, and its position is very natural there:

• deshalb bleibt die Jalousie heute offen

German often places time expressions in the middle of the clause, before the final adjective or complement.

This sounds normal and idiomatic. You could also move heute to the front for emphasis:

• Heute bleibt die Jalousie offen.

But in the original sentence, the focus is on the consequence introduced by deshalb, so heute stays later in the clause.

The sentence contains two main clauses:

1. Im Flur ist die Glühbirne kaputt
2. deshalb bleibt die Jalousie heute offen

The comma separates these two closely connected clauses.

A key point is that deshalb does not create a subordinate clause. The second part is still a normal main clause, which is why the verb comes early:

• deshalb bleibt ...

You could also write this as two sentences in many contexts:

• Im Flur ist die Glühbirne kaputt. Deshalb bleibt die Jalousie heute offen.