In meiner Signatur stehen mein Name und meine Telefonnummer.

Because in can take either the dative or the accusative, depending on the meaning:

• dative = location, being somewhere
• accusative = movement into somewhere

Here, the sentence describes where the name and phone number are located, so German uses the dative:

• in meiner Signatur = in my signature

Since Signatur is a feminine noun, its dative singular form with mein is meiner.

German often uses verbs like stehen, liegen, and hängen to describe where something is written or placed.

So stehen here does not literally mean that the name and phone number are physically standing up. It is a very common way to say that something is written or appears somewhere.

So:

• In meiner Signatur stehen mein Name und meine Telefonnummer. = My name and phone number are in my signature.

Using stehen sounds natural in German when talking about text on a page, screen, sign, document, or similar place.

Because the subject is plural:

• mein Name
• und meine Telefonnummer

Two things joined by und usually make a plural subject, so the verb must also be plural:

• singular: Mein Name steht in meiner Signatur.
• plural: Mein Name und meine Telefonnummer stehen in meiner Signatur.

That is why German uses stehen.

German main clauses follow the verb-second rule. That means the finite verb must be in the second position.

In this sentence, the first position is taken by:

• In meiner Signatur

So the verb must come next:

• In meiner Signatur stehen ...

Only after that do we get the subject:

• mein Name und meine Telefonnummer

This is normal German word order. If the subject came first, you could also say:

• Mein Name und meine Telefonnummer stehen in meiner Signatur.

That version is also correct.

Because these nouns are the subject of the sentence, so they are in the nominative case.

The subject is the thing doing the action, or in this case, the things that stand/appear in the signature.

So we need nominative forms:

• mein Name = nominative masculine singular
• meine Telefonnummer = nominative feminine singular

If you used meinen Namen, that would be accusative, which would be wrong here.

These are forms of the possessive word mein = my, and the ending changes depending on gender, number, and case.

Here are the forms used in this sentence:

• meiner Signatur

  • Signatur is feminine singular
  • after in with location, it is dative
  • so: meiner

• mein Name

  • Name is masculine singular
  • it is the subject, so nominative
  • so: mein

• meine Telefonnummer

  • Telefonnummer is feminine singular
  • it is also nominative
  • so: meine

So the endings are changing for grammatical reasons, not because the meaning of my changes.

Yes, that would be understandable, and grammatically it can work. But stehen is more idiomatic here when talking about written information.

Compare:

• stehen = written there, appearing there
• sind = are there

So sind is possible, but stehen sounds more natural in standard German for text in a signature, document, email, or similar context.

Not usually in this sentence. Here Signatur most naturally means a signature block, especially in an email or message — the section where your contact details appear.

If you mean your handwritten signature, German more often uses:

• Unterschrift

So:

• Signatur = often a digital/email signature or signature line
• Unterschrift = handwritten signature

In this sentence, Signatur strongly suggests something like an email signature.

Because mein already works like a determiner, similar to my in English. In German, you normally do not combine it with another article in this kind of phrase.

So German says:

• mein Name
• meine Telefonnummer

not:

• der mein Name
• die meine Telefonnummer

This is the same idea as in English: you say my name, not the my name.

Yes. German very often combines nouns into a single word.

So:

• Telefon
  • Nummer = Telefonnummer

This is completely normal in German. English often writes similar ideas as two words, but German commonly makes them into one compound noun.

Word-for-word, yes, that is close to the German structure. But natural English would not usually say that.

A more natural English rendering is:

• My name and phone number are in my signature.
• My name and phone number appear in my signature.

This is a good example of why German stehen should not always be translated literally as stand.