Die Lehrerin legt das Arbeitsblatt auf den Tisch.

Because Lehrerin is a feminine noun. In German, nouns have grammatical gender, and feminine nouns in the nominative singular often use the article die.

So here:

• die Lehrerin = the female teacher

If it were a male teacher, it would be:

• der Lehrer

The ending -in is a very common way to make a noun specifically female in German.

For example:

• der Lehrer = male teacher / teacher
• die Lehrerin = female teacher

The plural is:

• die Lehrerinnen = female teachers

So Lehrerin is built from Lehrer + -in.

Because the subject is die Lehrerin, which is she / the teacher in the third person singular.

The verb legen changes depending on the subject:

• ich lege
• du legst
• er/sie/es legt
• wir legen
• ihr legt
• sie/Sie legen

So with die Lehrerin, you need:

• Die Lehrerin legt ...

Legen means to lay, to put, or to place something somewhere. It usually implies that someone is moving an object to a position.

A useful contrast is:

• legen = to lay/put something down
• liegen = to be lying / to be located

So:

• Die Lehrerin legt das Arbeitsblatt auf den Tisch. = she puts it there
• Das Arbeitsblatt liegt auf dem Tisch. = it is lying there

This is a very common German verb pair:

• legen / liegen
• stellen / stehen
• setzen / sitzen

Because Arbeitsblatt is a neuter noun, so its nominative and accusative singular article is das.

Here it is:

• das Arbeitsblatt = the worksheet

In this sentence, das Arbeitsblatt is the direct object, and for a neuter noun in the accusative, the article still stays das.

So:

• nominative: das Arbeitsblatt
• accusative: das Arbeitsblatt

German often forms long compound nouns by joining smaller words together. Arbeitsblatt is made from:

• Arbeit = work
• Blatt = sheet/page

The -s- is a linking sound, often called a Fugen-s. It does not always have a meaning by itself; it just helps connect the parts of the compound naturally.

So:

• Arbeitsblatt = worksheet

German uses compounds very often, so getting used to them is important.

Because this sentence describes movement toward a destination.

German uses certain prepositions, including auf, with:

• accusative when there is movement to a place
• dative when there is location in a place

Here, the worksheet is being moved onto the table:

• auf den Tisch = onto the table

If the worksheet were already there, you would say:

• auf dem Tisch = on the table

So the contrast is:

• Sie legt das Arbeitsblatt auf den Tisch. = movement
• Das Arbeitsblatt liegt auf dem Tisch. = location

Because Tisch is a masculine noun, and after auf with movement, it takes the accusative case.

The masculine article changes like this:

• nominative: der Tisch
• accusative: den Tisch

That is why you get:

• auf den Tisch

This change happens only with masculine nouns. For comparison:

• auf den Stuhl from der Stuhl
• but auf das Bett stays das
• and auf die Lampe stays die

Yes, very often onto the table is the most precise English equivalent, because the German accusative here shows movement toward the surface of the table.

In natural English, people often still say on the table, even when movement is involved:

• She puts the worksheet on the table.

But if you want to notice the German grammar clearly, it helps to think:

• auf den Tisch = onto the table
• auf dem Tisch = on the table

Because standard German main clauses usually follow the verb-second rule, often called V2.

In this sentence:

• 1st element: Die Lehrerin
• 2nd element: legt

Then the rest follows:

• das Arbeitsblatt auf den Tisch

This does not mean the verb must always be the second word. It must be the second element.

For example:

• Die Lehrerin legt das Arbeitsblatt auf den Tisch.
• Heute legt die Lehrerin das Arbeitsblatt auf den Tisch.

In the second sentence, Heute is the first element, so the verb still comes second.

It is possible in some contexts, but it is not the most neutral or natural word order.

The most normal order here is:

• Die Lehrerin legt das Arbeitsblatt auf den Tisch.

German is flexible, but word order affects emphasis. Putting auf den Tisch before das Arbeitsblatt can sound marked or stylistically unusual unless there is a special reason to emphasize the destination.

So for learners, the basic pattern to remember is:

• subject + verb + object + place

Yes. You can tell because:

• it is in the nominative case
• the verb legt agrees with it
• it is the person doing the action

So:

• die Lehrerin = subject
• das Arbeitsblatt = direct object
• auf den Tisch = prepositional phrase showing destination

The verb form legt is present tense.

German often uses the simple present where English might use either:

• puts
• is putting

So this sentence can mean, depending on context:

• The teacher puts the worksheet on the table.
• The teacher is putting the worksheet on the table.

German does not need a separate is putting form here.

Then you would normally switch from legen to liegen, and from accusative to dative after auf:

• Das Arbeitsblatt liegt auf dem Tisch.

Notice the changes:

• legt → liegt
• auf den Tisch → auf dem Tisch

That is a very important German pattern:

• action of placing something: legen
  • accusative place
• state/location afterward: liegen
  • dative place