Trabajo en la empresa con mi hermana.

Spanish usually omits subject pronouns (like yo, tú, él) because the verb ending already shows who the subject is.

• trabajo = I work (first person singular)
• trabajas = you work
• trabaja = he / she / you (formal) work

So Trabajo en la empresa con mi hermana naturally means “I work at the company with my sister”. Adding yo (Yo trabajo…) is possible, but it’s only needed for emphasis or contrast:

• Yo trabajo en la empresa, pero él no.
  I work at the company, but he doesn’t.

In Spanish, the simple present (trabajo) can cover both:

• A general/habitual action:
  Trabajo en la empresa. → I work at the company. (in general)
• A current ongoing situation (especially with context):
  Ahora trabajo en la empresa. → Right now I’m working at the company.

If you really want to stress “right now, at this moment”, you can use the progressive:

• Estoy trabajando en la empresa. → I am working at the company (currently).

Because the verb is conjugated for yo (I):

• yo trabajo – I work
• tú trabajas – you (informal) work
• él / ella / usted trabaja – he / she / you (formal) work
• nosotros / nosotras trabajamos – we work
• ellos / ellas / ustedes trabajan – they / you all work

The sentence talks about I, so it uses trabajo.

These prepositions change the meaning:

• en la empresa = in/at the company (location)
  You are physically or organizationally in that company.
• para la empresa = for the company (for the benefit / as an employer)
  You might work for them even from home.
• a la empresa usually goes with motion verbs:
  Voy a la empresa. → I go to the company.

So Trabajo en la empresa focuses on where you work (at that place/organization).
Trabajo para la empresa focuses more on who you work for.

Spanish uses definite articles (el, la, los, las) more than English:

• la empresa = the company (a specific one, known from context)
• una empresa = a company (not specific)

Trabajo en la empresa implies you and your listener both know which company you mean (e.g., your usual employer).

Just saying Trabajo en empresa (without an article) is not natural Spanish in this context.

Yes, that word order is also correct:

• Trabajo en la empresa con mi hermana.
• Trabajo con mi hermana en la empresa.

Both usually mean the same: I work at the company with my sister.

Subtle nuance:

• Placing con mi hermana next to trabajo can slightly emphasize with my sister (the company is more like background information).
• But in most everyday conversations, they’re understood the same.

By itself, con mi hermana is a bit vague. It simply says you work “with my sister”, which:

• Often is understood as: you both work at the same company.
• It does not necessarily mean the same department, job, or project.

If you want to be clearer:

• Trabajo en la misma oficina que mi hermana.
  I work in the same office as my sister.
• Trabajo en el mismo departamento que mi hermana.
  I work in the same department as my sister.

In Latin American Spanish:

• empresa is the most common and neutral term for company / business.
• compañía is also used, sometimes a bit more formal or in certain names:
  • Compañía de seguros – insurance company
  • La compañía XYZ – the XYZ company

In most everyday situations, empresa is the default, natural word to use for company.

That’s a different idea. You’d say:

• Trabajo en la empresa de mi hermana.
  I work at my sister’s company.

Compare:

• Trabajo en la empresa con mi hermana.
  I work at the company with my sister (she also works there).
• Trabajo en la empresa de mi hermana.
  I work at my sister’s company (she owns it or it’s clearly “hers”).

In Spanish, mi (my) does not change for gender, only for number:

• mi hermana – my sister (singular, feminine)
• mi hermano – my brother (singular, masculine)
• mis hermanas – my sisters (plural)
• mis hermanos – my brothers / my siblings (plural)

So mi is used for both masculine and feminine singular nouns; mis is for plurals.

You need to make hermana plural:

• Trabajo en la empresa con mis hermanas.

Changes:

• mi → mis (because it’s now plural)
• hermana → hermanas (plural feminine)

Yes, context can give it that reading. Spanish present tense is flexible:

• Without extra context, Trabajo en la empresa con mi hermana sounds like a regular job (a permanent or usual situation).
• With time expressions, it can refer to a temporary situation:
  • Esta semana trabajo en la empresa con mi hermana.
    This week I’m working at the company with my sister.

If you really want to stress the temporary/action-right-now idea, you could use:

• Esta semana estoy trabajando en la empresa con mi hermana.

Approximate pronunciation (Latin American):

• trabajo: tra-BA-ho
  
  • tra like “tra” in “trouble” (but shorter)
  • BA stressed, like “BAH”
  • jo: the j is a harsh h sound (like the h in “house” but stronger, from the throat): -ho
• hermana: er-MA-na
  
  • Starting h is silent, so er sounds like English “air” (but shorter)
  • Stress on MA: er-MA-na

empresa is feminine, so it takes la in the singular and las in the plural:

• la empresa – the company
• las empresas – the companies
• una empresa grande – a big company

In general, many nouns ending in -a are feminine, though there are exceptions. You learn gender with each noun as you go, but empresa is reliably feminine.