Ich kann nicht gleichzeitig lesen und fernsehen.

Because können is the infinitive, meaning to be able to / can.

In the sentence, the verb has to agree with ich (I), so it becomes:

• ich kann = I can
• du kannst = you can
• er/sie/es kann = he/she/it can

So Ich kann ... is the correct conjugated form.

Because kann is a modal verb. In German, when you use a modal verb like können, the main action verb usually goes to the end in the infinitive form.

So the pattern is:

• Ich kann lesen. = I can read.
• Ich kann fernsehen. = I can watch TV.

If there are two main verbs, both infinitives stay at the end:

• Ich kann nicht gleichzeitig lesen und fernsehen.

That is very normal German word order.

Here, nicht is negating the idea of doing the two actions simultaneously.

So the sentence means:

• I cannot read and watch TV at the same time.

It does not mean that the speaker cannot read at all or cannot watch TV at all. It means they cannot do both together.

That is why nicht comes before gleichzeitig here: it naturally negates the whole phrase gleichzeitig lesen und fernsehen.

Not naturally in this meaning.

Ich kann nicht gleichzeitig lesen und fernsehen is the normal way to say:

• I can’t read and watch TV at the same time.

If you move nicht, the meaning can become awkward or unclear. German is quite sensitive to nicht placement, because it changes what is being negated.

So for this sentence, nicht gleichzeitig is the best and most idiomatic wording.

Gleichzeitig means at the same time / simultaneously.

It is an adverb. In this sentence, it sits before the infinitives it relates to:

• ... nicht gleichzeitig lesen und fernsehen.

That placement is very natural because gleichzeitig describes how the two actions happen.

You may also hear similar sentences like:

• Ich arbeite und höre gleichzeitig Musik.
• Man kann nicht gleichzeitig reden und essen.

Because fernsehen is a verb meaning to watch TV.

It is formed from:

• fern = far / distant
• sehen = to see

But as a verb, it is written as one word: fernsehen.

Important: it is a separable verb when conjugated on its own:

• Ich sehe fern. = I watch TV.

But with a modal verb like kann, it stays together in the infinitive:

• Ich kann fernsehen.

So in your sentence, fernsehen remains one word because it is at the end as an infinitive.

Because here it is a verb, and German verbs are normally lowercase.

Compare:

• fernsehen = to watch TV → verb, lowercase
• das Fernsehen = television / TV broadcasting / watching television as a noun → noun, capitalized

In your sentence, it is clearly a verb:

• ... lesen und fernsehen.

So lowercase is correct.

Because after a modal verb like können, German uses the bare infinitive, not zu + infinitive.

So you say:

• Ich kann lesen.
• Ich kann fernsehen.

Not:

• Ich kann zu lesen.
• Ich kann zu fernsehen.

This is similar to English, where we say I can read, not I can to read.

Yes. German can join two infinitives with und just like English joins two verbs with and.

So:

• lesen und fernsehen = read and watch TV

Because both verbs depend on kann, they both stay in the infinitive.

You could do the same with many other verbs:

• Ich kann singen und tanzen.
• Wir wollen essen und reden.

Yes, in everyday German, TV schauen or Fernsehen schauen may be heard, depending on region and style. But fernsehen is a very standard and common verb.

So these are similar:

• Ich kann nicht gleichzeitig lesen und fernsehen.
• Ich kann nicht gleichzeitig lesen und TV schauen.

The version with fernsehen is especially useful for learners because it is a basic, standard verb.

A useful way to see it is:

• Ich = subject
• kann = conjugated modal verb in second position
• nicht gleichzeitig = negation + adverb
• lesen und fernsehen = infinitive verbs at the end

So the structure is:

Subject + modal verb + other information + infinitive(s)

That pattern appears very often in German:

• Ich kann heute nicht kommen.
• Sie will morgen arbeiten.
• Wir müssen jetzt gehen.

Your sentence follows that pattern exactly.

Usually it means the speaker is not able to do both at once, in a practical sense.

So it could mean:

• I’m not capable of doing both simultaneously.
• I can’t manage both at the same time.

It does not have to mean a dramatic physical inability. In everyday speech, ich kann nicht often simply means I can’t manage / I’m unable to in that situation.

So here it sounds very natural and ordinary.