Meine Nachbarin schraubt die neue Glühbirne in die Lampe.

Because Nachbarin is a feminine noun meaning female neighbor.

• mein is the base form of my
• before a feminine noun in the nominative singular, it becomes meine

So:

• mein Nachbar = my male neighbor
• meine Nachbarin = my female neighbor

The -in ending on Nachbarin is a very common way to form a feminine noun for a person in German.

The ending -in often marks a female person in German.

Examples:

• der Nachbar = the male neighbor
• die Nachbarin = the female neighbor
• der Lehrer = the male teacher
• die Lehrerin = the female teacher

So Nachbarin specifically tells you the neighbor is a woman.

In a normal German main clause, the finite verb usually comes in position 2.

This sentence is structured like this:

• Meine Nachbarin = subject
• schraubt = finite verb
• die neue Glühbirne = object
• in die Lampe = prepositional phrase

So the pattern is:

Subject + verb + other information

That is one of the most basic German word order rules.

Because the subject is Meine Nachbarin, which is third person singular: she.

The verb schrauben means to screw. Its present-tense forms include:

• ich schraube
• du schraubst
• er/sie/es schraubt
• wir schrauben
• ihr schraubt
• sie/Sie schrauben

Since meine Nachbarin = she, the correct form is schraubt.

Because Glühbirne is a feminine noun, and here it is in the accusative singular.

For feminine nouns, the definite article is:

• die in the nominative singular
• die in the accusative singular

So in this sentence:

• die neue Glühbirne = the new light bulb

Even though the case is accusative, the feminine article still stays die.

There are two big clues:

1. Meaning: it is the thing being screwed in
2. Verb pattern: schrauben takes a direct object here

So:

• Meine Nachbarin = the person doing the action = subject
• die neue Glühbirne = the thing affected by the action = direct object

In English, this is similar to:

• My neighbor screws in the new light bulb

The light bulb receives the action.

Because adjective endings in German depend on:

• the article before the noun
• the noun’s gender
• the case

Here we have:

• die = definite article
• Glühbirne = feminine singular
• accusative singular

After a definite article, the adjective takes the weak ending. For feminine accusative singular, that ending is -e.

So:

• die neue Glühbirne

Compare:

• der neue Tisch = the new table
• die neue Lampe = the new lamp
• das neue Buch = the new book

Because in is a two-way preposition. It can take either:

• accusative for movement toward/into something
• dative for location inside something

Here, the light bulb is being moved into the lamp, so German uses accusative:

• in die Lampe = into the lamp

If you were describing location, you would use dative:

• in der Lampe = in the lamp

So the contrast is:

• Sie schraubt die Glühbirne in die Lampe. = She screws the bulb into the lamp.
• Die Glühbirne ist in der Lampe. = The bulb is in the lamp.

Yes, that is the most literal sense here.

In natural English, you might say:

• into the lamp
• into the socket
• in the lamp

German often expresses the motion more explicitly with in + accusative.

So in die Lampe shows the direction of the action: the bulb is being screwed into the lamp.

Because German articles repeat according to the noun they belong to.

In this sentence:

• die neue Glühbirne
• die Lampe

Both Glühbirne and Lampe are feminine singular, so both use die in the accusative singular.

This does not mean the same die is doing two jobs. Each one belongs to its own noun phrase.

Also, die can mean different things in German depending on context:

• feminine singular the
• plural the

Here, both are feminine singular, not plural.

Yes. Glühbirne is the standard everyday word for light bulb.

It is made of:

• glüh- related to glowing
• Birne = pear

Historically, the shape suggested a pear, which is why the word looks a bit funny literally.

In everyday use, just think:

• die Glühbirne = light bulb

You may also hear Lampe in casual speech for the bulb, but strictly speaking:

• die Lampe = lamp/light fixture
• die Glühbirne = light bulb

Yes, very often German would use einschrauben for this idea.

For example:

• Meine Nachbarin schraubt die neue Glühbirne in die Lampe.
• Meine Nachbarin schraubt die neue Glühbirne in die Lampe ein.

Both can work, depending on style and context. The version with einschrauben makes the idea of screwing in especially clear.

Because einschrauben is a separable verb, in a main clause it splits:

• Sie schraubt die Glühbirne ein.

Your sentence uses plain schrauben plus in die Lampe, which is also understandable and natural.

Yes, but the finite verb still stays in second position in a main clause.

For example, you could say:

• Die neue Glühbirne schraubt meine Nachbarin in die Lampe.
• In die Lampe schraubt meine Nachbarin die neue Glühbirne.

These are grammatical, but they place emphasis on different parts of the sentence.

The most neutral version is the original:

• Meine Nachbarin schraubt die neue Glühbirne in die Lampe.

That is probably the best form for a learner to use first.