Hij probeert vaker te pauzeren en zet zijn telefoon soms op stiltestand.

In Dutch, many verbs that mean trying, planning, beginning, forgetting, hoping etc. are followed by te + infinitive when you add another verb.

Proberen normally takes te + infinitive:

• Ik probeer te slapen. – I’m trying to sleep.
• Hij probeert te stoppen met roken. – He’s trying to stop smoking.

So:

• Hij probeert vaker te pauzeren.
  = He tries to take breaks more often.

Without te (hij probeert vaker pauzeren) is not standard Dutch; it sounds wrong or at least very off to native speakers.

Yes, you can, and it’s quite natural:

• Hij probeert vaker te pauzeren.
• Hij probeert vaker pauzes te nemen.

Both mean essentially the same thing in this context.

Nuance:

• te pauzeren uses the verb pauzeren (“to pause / take a break”).
• pauzes te nemen uses the noun pauzes and the verb nemen (“to take breaks”).

In everyday speech both are fine. Pauzes nemen is maybe slightly more common in informal conversation, but pauzeren is perfectly normal and clear.

Vaker is the normal comparative form of vaak (“often”).

• vaak = often
• vaker = more often

You do not normally say meer vaak in Dutch. That sounds like a literal translation from English.

So:

• Hij pauzeert vaak. – He takes breaks often.
• Hij pauzeert vaker. – He takes breaks more often.
• Hij probeert vaker te pauzeren. – He tries to take breaks more often.

Use vaker, not meer vaak.

In Dutch, adverbs of frequency like vaak, vaker, soms, altijd usually come before the infinitive if there is a te + infinitive construction:

• Hij probeert vaker te pauzeren.
• Ik probeer altijd op tijd te komen.
• We proberen soms eerder te vertrekken.

Hij probeert te pauzeren vaker sounds unnatural. The typical order is:

[subject] + [finite verb] + [adverb] + te + [infinitive]
→ Hij probeert vaker te pauzeren.

The subject hij applies to both parts of the sentence:

• Hij probeert vaker te pauzeren
• (Hij) zet zijn telefoon soms op stiltestand.

In Dutch (as in English), when you have one subject and two verbs joined by en, you don’t need to repeat the subject:

• Hij kookt en eet. – He cooks and eats.
• Hij werkt veel en slaapt weinig. – He works a lot and sleeps a little.

So:

• Hij probeert vaker te pauzeren en zet zijn telefoon soms op stiltestand.
  = He tries to take breaks more often and (he) sometimes puts his phone on silent mode.

The subject hij is understood for both verbs.

Both are grammatical; they just represent a slightly different structure.

1. As a full separate clause, you would say:

   • Hij zet soms zijn telefoon op stiltestand.
     (subject hij
     • verb zet in second position)

2. In the original sentence, this clause is directly connected to the first one and shares the same subject:

   • Hij probeert vaker te pauzeren en zet zijn telefoon soms op stiltestand.

Here, the hij is not repeated, but the verb zet still appears as if the sentence were:

• Hij zet zijn telefoon soms op stiltestand.

So in the coordinated structure:

• Hij [probeert vaker te pauzeren] en [zet zijn telefoon soms op stiltestand].

If you started a new sentence, you’d normally include the hij again:

• Hij probeert vaker te pauzeren. Hij zet soms zijn telefoon op stiltestand.

Yes, soms is fairly flexible. The most natural positions are:

• Hij zet soms zijn telefoon op stiltestand.
• Hij zet zijn telefoon soms op stiltestand.

Both are common; many speakers slightly prefer the second one in this exact context.

Hij zet zijn telefoon op stiltestand soms is understandable, but it sounds less natural and more marked. In Dutch, adverbs like soms usually appear before the phrase they modify, not at the very end of the clause.

In Dutch, when you talk about turning a device to a certain mode or state, you usually use op:

• je telefoon op stiltestand zetten – to put your phone on silent mode
• de tv op mute zetten – to put the TV on mute
• de thermostaat op 20 graden zetten – to set the thermostat to 20 degrees
• de wasmachine op kort programma zetten – to set the washing machine to a short program

So op here means “onto / to (a certain setting)”.
In stiltestand would sound incorrect in this meaning.

Stiltestand is a compound noun:

• stilte = silence
• stand = position/setting/mode

So stiltestand = “silent mode”.

It is understandable and used, though in everyday speech you’ll often also hear:

• op stil
  
  • Hij zet zijn telefoon soms op stil.
    (literally: he sometimes puts his phone on silent)

Other very common expressions are:

• zijn geluid uitzetten – to turn off its sound
• zijn telefoon op stil zetten – to put his phone on silent
• vliegtuigstand – airplane mode

So op stiltestand is correct and clear, but op stil is at least as common in casual speech.

Both zijn telefoon and de telefoon are possible, but they don’t sound the same:

• zijn telefoon – his phone (explicitly his own device)
• de telefoon – the phone (more general/less personal)

In this sentence, the idea is about his personal habit and his own phone, so zijn telefoon is more natural.

If you say:

• Hij zet de telefoon soms op stiltestand.

it could sound like you’re talking about a shared phone (maybe an office phone), or just “the phone” in the situation, not necessarily his personal mobile.