Das Telefon klingelt ständig, also mache ich es am besten stumm.

Because Telefon is a neuter noun in German, so its definite article is das.

• das Telefon = the phone
• In the nominative case, neuter nouns take das

You simply have to learn the gender with the noun:

• das Telefon
• der Tisch
• die Lampe

This is why the later pronoun is also es, because es is the pronoun used for neuter nouns.

Both verbs exist, but they are used a bit differently.

• klingeln often means to ring in the sense of a phone, doorbell, alarm, etc.
• klingen usually means to sound in a broader sense, especially how something sounds.

So:

• Das Telefon klingelt. = The phone is ringing.
• Das klingt gut. = That sounds good.

For a phone, klingeln is the most natural choice.

Ständig means something like:

• constantly
• all the time
• continually

In this sentence, it suggests the phone keeps ringing again and again, enough to be annoying.

A learner should know that ständig is common in everyday German. Similar words include:

• immer wieder = again and again
• die ganze Zeit = the whole time
• andauernd = constantly / continually

Depending on context, ständig can sound a little like too often or annoyingly often.

No, not in this sentence.

German also often means:

• so
• therefore
• well then

Here, also connects cause and result:

• Das Telefon klingelt ständig, also ...
• The phone keeps ringing, so ...

This is a very common false friend for English speakers, because English also usually means too / as well, but German also usually does not mean that.

Examples:

• Ich bin müde, also gehe ich ins Bett. = I’m tired, so I’m going to bed.
• Er ist krank, also bleibt er zu Hause. = He’s sick, so he’s staying home.

Because in a main clause, German usually follows the verb-second rule.

That means the finite verb must come in the second position. Here:

• also takes the first position
• mache must come next
• then ich

So:

• ..., also mache ich es am besten stumm. ✔
• ..., also ich mache es am besten stumm. ✘

This is one of the most important German word order rules.

Compare:

• Heute gehe ich nach Hause.
• Dann rufe ich an.
• Deshalb bleibe ich hier.

In all of these, the first element is not the subject, so the verb still comes second.

Es refers back to das Telefon.

Since Telefon is neuter (das Telefon), the matching pronoun is es:

• das Telefon → es

So:

• mache ich es stumm = I make it silent / I mute it

This is very natural in German. Once a noun has already been mentioned, it is often replaced by a pronoun.

Yes. This is a common German structure:

machen + object + adjective

It means to make something become a certain state.

So:

• ich mache es stumm = I make it silent / I mute it

Other examples:

• Ich mache das Fenster auf. = I open the window.
• Sie macht die Tür zu. = She closes the door.
• Er macht das Licht aus. = He turns off the light.
• Wir machen das Zimmer sauber. = We make the room clean / clean the room.

With stumm, the idea is that the phone is put into silent mode.

Yes, and in many situations that may even sound especially natural.

Both are possible, but the nuance can differ a little:

• es stumm machen = to mute it / make it silent
• es stumm stellen = to set it to silent

For phones, many speakers would say things like:

• Ich stelle mein Handy auf lautlos.
• Ich mache mein Handy stumm.

So the sentence is correct and natural, but there are several idiomatic ways to express the same idea.

Am besten literally means best, but here it has the sense of:

• probably best
• best to
• the best thing to do is

So:

• also mache ich es am besten stumm means something like
• so I’d better mute it
• so it’s probably best if I mute it

It softens the statement a little and makes it sound like a practical decision.

Examples:

• Du gehst am besten jetzt. = You’d better go now.
• Wir rufen am besten morgen an. = We’d probably better call tomorrow.

Because adverbial expressions like am besten are often placed in the middle field of the sentence, after the pronoun/object and before the final adjective or other complements.

In:

• also mache ich es am besten stumm

the order is:

• also = connector in first position
• mache = finite verb in second position
• ich = subject
• es = object pronoun
• am besten = adverbial phrase
• stumm = result/state

German word order in the middle of the sentence is flexible, but this version sounds natural and idiomatic.

They are close, but not always identical.

• stumm = silent, muted
• lautlos = soundless / silent

For phones, both can work, but they are used slightly differently:

• das Handy stumm machen = mute the phone
• das Handy auf lautlos stellen = set the phone to silent

In everyday speech about phone settings, lautlos is extremely common.
But stumm machen is also very natural, especially when talking about muting something.

Because German does not need an infinitive structure here. The sentence uses a normal finite verb:

• mache ich es ... stumm = I make it ... silent

English often uses structures like:

• I’d better mute it
• I should mute it

German instead expresses the idea directly with:

• Ich mache es am besten stumm.

So the grammar is different even though the meaning is similar.

It is neutral everyday German.

Nothing in it is especially formal or especially casual. It would fit normal spoken German very well.

A few notes:

• Telefon is neutral and standard.
• In real life, many people might say Handy if they mean a mobile phone.
• The structure am besten makes it sound practical and conversational.

For example:

• Mein Handy klingelt ständig, also mache ich es am besten stumm.

That may sound even more everyday if the speaker clearly means a cell phone.

Normally, the comma before also should be kept here.

The sentence joins two main clauses:

• Das Telefon klingelt ständig
• also mache ich es am besten stumm

In standard written German, a comma is commonly used to separate them, especially when the second clause is introduced by a connector like also.

So the written form with the comma is the correct and natural choice.

Yes, but the original position is the most natural one.

You have:

• Das Telefon klingelt ständig.

That is the normal way to say it.

Other word orders are possible for emphasis, for example:

• Ständig klingelt das Telefon.

This puts more focus on ständig and may sound more dramatic or emphatic, like:

• The phone keeps ringing all the time.

German word order is flexible, but changing it often changes emphasis rather than basic meaning.