Learn Spanish (Latin America): Necesitamos el presupuesto para el viernes para aumentar las ventas. - We need the budget by Friday to increase sales.

It is doing two different jobs that you are learning in this lesson! The first one, para el viernes, shows a deadline (by Friday). The second one, para aumentar, shows a purpose (in order to increase). Para is very flexible and is the correct choice for both situations.

Why is aumentar (to increase) in its unconjugated form?

In Spanish, when a verb immediately follows a preposition like para, it must stay in its infinitive (unconjugated) form. Because of this rule, para aumentar naturally translates to "in order to increase" or simply "to increase."

Why do we say el viernes instead of just viernes?

In Spanish, you almost always need to use the definite article (el or los) before days of the week when you are talking about something happening on, or by, a specific day. So, para el viernes literally translates as "by the Friday."

Would it be wrong to use por instead of para in this sentence?

Yes, it would change the meaning completely. If you said por el viernes, it would sound like you need the budget "because of Friday" or "during Friday," rather than setting a strict deadline. For deadlines and goals, you must always use para.