Learn Hardcore German: Ich lege das Heft auf den Tisch.

Since the subject is ich (I), you must use the ich-form lege. Legt would go with er/sie/es or ihr, and legen with wir, sie, or formal Sie.

Can this German sentence mean both “I put the notebook on the table” and “I am putting the notebook on the table”?

Yes. German normally uses one present tense form for both the English simple present and present continuous.

So Ich lege das Heft auf den Tisch can mean:

I put the notebook on the table.
I am putting the notebook on the table.

Context (and sometimes adverbs like gerade = right now) tells you whether it is a one-time action happening now or a repeated action.

Why is Heft capitalised?

In German, all nouns are capitalised, regardless of where they appear in the sentence.

das Heft – the notebook / exercise book
der Tisch – the table

Verbs (lege), adjectives, and other parts of speech are normally written with a lowercase initial letter, unless they begin a sentence or are part of a proper name.

Why is it das Heft but den Tisch?

Two different things are happening here:

Gender of the noun
- Heft has neuter grammatical gender → nominative singular article: das Heft.
- Tisch has masculine grammatical gender → nominative singular article: der Tisch.
Case (role in the sentence)
- das Heft is the direct object of legen (what is being put). Direct objects take the accusative case. For neuter nouns, nominative and accusative are the same: das.
- den Tisch is governed by the preposition auf, which here requires the accusative (because of motion, see below). Masculine accusative of der Tisch is den Tisch.

So Heft is neuter (hence das), and Tisch is masculine and in the accusative after auf, so den.

Why is it auf den Tisch and not auf dem Tisch?

Auf is a “two-way preposition” (Wechselpräposition). With these prepositions, the case depends on the meaning:

Accusative (here: auf den Tisch) → movement towards a place (direction).
Dative (here: auf dem Tisch) → something is located at a place (no movement).

In Ich lege das Heft auf den Tisch, there is movement onto the table, so you use the accusative: den Tisch.

If you were describing location instead of movement, you would use the dative:

Das Heft liegt auf dem Tisch. – The notebook is (lying) on the table.

So when exactly would I say auf dem Tisch instead?

Use auf dem Tisch (dative) whenever you are talking about something being already on the table, with no movement into that position:

Das Heft liegt auf dem Tisch. – The notebook is lying on the table.
Die Tassen stehen auf dem Tisch. – The cups are standing on the table.
Was ist auf dem Tisch? – What is on the table?

As soon as you describe putting, moving, laying, placing something onto the table, you switch to auf den Tisch (accusative):

Ich stelle das Glas auf den Tisch. – I put/stand the glass on the table.
Ich lege das Handy auf den Tisch. – I put/lay the phone on the table.

Are das Heft and den Tisch both accusative? Doesn’t that cause confusion?

Yes, both das Heft and den Tisch are in the accusative case, but they have different grammatical roles:

das Heft – direct object of the verb legen (what is being put).
den Tisch – object of the preposition auf (destination of the movement).

German distinguishes them by preposition plus case vs bare case:

The preposition auf clearly marks den Tisch as its own phrase (auf den Tisch).
Das Heft appears directly after the verb as the “thing being acted on”.

Native speakers do not confuse them because the structure Verb + object + prepositional phrase is very clear:
[Ich] [lege] [das Heft] [auf den Tisch].

Could I change the word order, for example Ich lege auf den Tisch das Heft or Auf den Tisch lege ich das Heft?

Some rearrangements are possible and grammatically correct, but they sound more or less natural:

Ich lege das Heft auf den Tisch. – Neutral, most common.
Ich lege auf den Tisch das Heft. – Grammatically correct but sounds unusual and marked; you would normally avoid this order.
Auf den Tisch lege ich das Heft. – Also correct; this puts emphasis on auf den Tisch (“onto the table” in particular).

German allows relatively flexible word order in the “middle field”, but:

The conjugated verb (lege) must stay in second position in a main clause.
Pronouns usually come before full noun phrases.
The standard, natural order here is exactly what you have: Ich lege das Heft auf den Tisch.

Why do we use legen here and not verbs like stellen, setzen, or legen versus liegen?

German has several “position verbs” that are more specific than English:

legen – to lay something down flat (horizontally).
stellen – to stand something upright (vertically).
setzen – to seat someone / to sit someone down.
liegen – to lie (already lying, no movement).
stehen – to stand (already standing, no movement).
sitzen – to sit (already sitting, no movement).

Here, you’re placing a notebook, which normally ends up lying flat on a surface, so legen is the natural choice:

Ich lege das Heft auf den Tisch. – I lay/put the notebook (so that it lies) on the table.
After that: Das Heft liegt auf dem Tisch. – The notebook is lying on the table.

If you put a bottle on the table so that it stands, you would use:

Ich stelle die Flasche auf den Tisch. – I put/stand the bottle on the table.
Die Flasche steht auf dem Tisch. – The bottle is standing on the table.

Can I drop the article and say Ich lege Heft auf den Tisch?

No, that would be incorrect in standard German. Unlike English, German normally needs an article (or another determiner like mein, dieses, etc.) with singular countable nouns.

You have options like:

Ich lege das Heft auf den Tisch. – I put the notebook on the table.
Ich lege ein Heft auf den Tisch. – I put a notebook on the table.
Ich lege mein Heft auf den Tisch. – I put my notebook on the table.

Leaving the article out with a singular count noun (Heft) sounds foreign or telegraphic and is usually only okay in headlines or notes, not in normal sentences.

How do I pronounce Ich and Tisch? They look similar at the end.

Both words use the so‑called “ich-sound” (ich-Laut), a soft sound that doesn’t exist in English.

Ich – roughly: [ɪç]
- Start with a short i as in “sit”, then let the air pass through a slightly spread, tense mouth with your tongue near the hard palate. It is not like English sh or k.
Tisch – roughly: [tɪʃ] in many accents, but in standard pronunciation it’s closer to [tɪʃ] with a sound between English sh and the ich-Laut. In practice, many learners approximate it with “tish”, which is widely understood.

So:

Ich – similar to “ish” but with the tongue more to the front and softer.
Tisch – like “tish”.

How would I say this sentence in the past tense in German?

You have two main options:

Perfect tense (spoken past; most common in conversation)
- Ich habe das Heft auf den Tisch gelegt. – I put / have put the notebook on the table.
  Structure: haben (conjugated) + past participle gelegt at the end.
Preterite/simple past (more written, narrative style for most verbs)
- Ich legte das Heft auf den Tisch. – I put the notebook on the table.
  This is grammatically correct but sounds literary or old-fashioned in everyday speech for a verb like legen.

In normal spoken German, Ich habe das Heft auf den Tisch gelegt is what you’d usually use.