Learn Hardcore German: Im Unterricht sehe ich meinen Mitschüler manchmal heimlich auf sein Handy schauen. - In class I sometimes see my male classmate secretly look at his phone.

German main clauses follow the verb‑second rule: the conjugated verb must be in second position, but anything can stand in first position (subject, time phrase, object, etc.).

Here, Im Unterricht (“during class”) is put in first position to set the scene/time and to emphasize when this happens.
Because first position is already taken by Im Unterricht, the verb sehe must come second, and the subject ich moves after the verb:

Im Unterricht (1st) sehe (2nd) ich (3rd) …

If you started with Ich, you’d get:

Ich sehe im Unterricht meinen Mitschüler …

Both are correct; the choice just changes the emphasis slightly.

Why is it sehe ich and not ich sehe in this sentence?

This is a direct result of the verb‑second rule explained above.

When Ich is in first position, you say: Ich sehe …
When a different element (here: Im Unterricht) occupies first position, the verb still has to be second, so you get: Im Unterricht sehe ich …

So the pattern is:

Ich sehe meinen Mitschüler …
Im Unterricht sehe ich meinen Mitschüler …

The word order change is grammar‑driven, not a change in meaning.

What exactly is im, and why not just say in dem Unterricht?

im is a standard contraction of in dem:

in (preposition “in”)
dem (dative singular of der, here for masculine noun Unterricht)
in dem Unterricht → im Unterricht

You usually must use the dative with in when it expresses a location or a time span:

im Unterricht = “during class / in the lesson” (dative)
Compare: in der Schule, im Zimmer, im Sommer

You could say in dem Unterricht, but in everyday spoken and written German the contracted form im is overwhelmingly preferred.

Which case is meinen Mitschüler, and why is it meinen and not mein?

meinen Mitschüler is in the accusative case as the direct object of the verb sehe (“I see whom? → meinen Mitschüler”).

Mitschüler is masculine singular.
The possessive mein must agree in gender, number, and case with the noun.

For masculine singular:

Nominative: mein Mitschüler (subject)
Accusative: meinen Mitschüler (direct object)

Since Mitschüler is what you see (the object), accusative is required → meinen Mitschüler.

Why is it sein Handy when the subject is ich? Shouldn’t it be mein Handy?

The possessive pronoun refers to the owner of the thing, not to the subject of the sentence.

Subject: ich (“I”) – the person who sees.
The phone belongs to meinen Mitschüler (my classmate).
For a masculine singular person (er), the possessive is sein.

So:

sein Handy = his phone (the classmate’s phone)
mein Handy = my phone (the speaker’s phone)

The sentence means: I see my classmate secretly looking at *his phone*, not at mine.

Why is the preposition auf used with sein Handy, and which case does it take here?

In the phrase auf sein Handy schauen, auf is used with the verb schauen to mean “to look at” something.

With schauen (auf …), auf governs the accusative:

auf sein Handy schauen – to look at his phone (accusative)
Template: auf + Akkusativ with verbs of looking:
- auf die Uhr schauen (look at the clock)
- auf den Bildschirm schauen (look at the screen)

You don’t see the case difference here because sein Handy is neuter and has the same form in nominative/accusative, but the rule is still “auf + accusative” in this expression.

Why does the sentence have both sehe and schauen? Isn’t one verb enough?

This is a very common perception + infinitive structure in German.

Pattern:

jemanden + Verb (sehen/hören/fühlen) + Infinitive
“to see/hear/feel someone do something”

In the example:

sehe = the perception verb (what I do: I see)
schauen = the action the classmate is doing (he looks at his phone)

So:

Ich sehe meinen Mitschüler auf sein Handy schauen.
= “I see my classmate look(ing) at his phone.”

It’s similar to English: I see him look at his phone, where English also has two verbs (see + look).

Why is schauen at the very end of the sentence?

In main clauses, non‑finite verbs (infinitives, participles) typically go to the end of the sentence.

The structure here is:

Front: Im Unterricht
Finite verb: sehe
Middle: ich meinen Mitschüler manchmal heimlich auf sein Handy
End: schauen (infinitive)

This “kick” of the infinitive to the end is standard German word order:

Ich sehe ihn das Auto waschen.
Wir hören die Nachbarn laut Musik spielen.
Im Unterricht sehe ich meinen Mitschüler auf sein Handy schauen.

Why is there no comma before auf sein Handy schauen?

Because auf sein Handy schauen is part of a bare infinitive construction that depends directly on sehe:

Ich sehe [meinen Mitschüler auf sein Handy schauen].

There is:

no “zu” before the infinitive, and
no subordinator like dass, weil, wenn etc.

In such sehen/hören/fühlen + Akkusativ + Infinitiv constructions, you do not put a comma:

Ich höre ihn laut lachen.
Wir sehen sie tanzen.

So here: no comma before auf sein Handy schauen.

Why is the adverb order manchmal heimlich and not heimlich manchmal?

Both manchmal and heimlich are adverbs, but they describe different things:

manchmal = frequency (“sometimes”) – how often I see this.
heimlich = manner (“secretly”) – how he looks at his phone.

In German, a common (not absolute) tendency is to place:

Adverbs of frequency/degree before
Adverbs of manner

So manchmal heimlich sounds natural:

Ich sehe ihn manchmal heimlich auf sein Handy schauen.

Heimlich manchmal would sound awkward and might even be confusing in most contexts. You could move manchmal to other positions (e.g. directly after sehe), but the given order is very typical.

What nuance does heimlich add here?

heimlich means “secretly, on the sly, without being noticed.”

In this sentence, it suggests that:

the classmate is trying not to be seen using his phone,
maybe because it’s not allowed during class,
he is doing it discreetly, perhaps under the desk or while the teacher is not looking.

Synonyms in English: secretly, stealthily, on the sly, furtively.

What is the difference between im Unterricht and something like im Klassenzimmer or in der Klasse?

All relate to school, but they emphasize different things:

im Unterricht
- literally: “in the lesson / during class”
- focuses on the activity of teaching/learning, the time when class is happening.
im Klassenzimmer
- “in the classroom”
- focuses on the physical room, not necessarily that a lesson is going on.
in der Klasse
- can mean “in the class (group of students)” or sometimes “in class” in a more general, looser way.
- Context is needed; it’s a bit less precise.

In this sentence, im Unterricht is best because the idea is “during the lesson,” when phone use is usually forbidden.

Could we replace schauen with other verbs like gucken or anschauen, and would the sentence change?

Yes, but there are small differences in register and typical phrasing:

auf sein Handy schauen – neutral/standard, very common.
auf sein Handy gucken – more colloquial, often used in everyday speech.
sein Handy anschauen – also good; here you normally drop “auf”:
- Im Unterricht sehe ich meinen Mitschüler manchmal heimlich *sein Handy anschauen.*

All three are understandable and natural, but:

schauen (auf) and gucken (auf) strongly suggest “to look at (a screen, object, etc.)”.
anschauen frames the phone more as an object being looked at, but the meaning in context is almost the same: he is using/looking at his phone.

So you can vary the verb, but the original auf sein Handy schauen is a very typical, neutral standard choice.