Qual è la differenza tra "para" e "a" e "por" ?Sentiti libero di rispondere con un esempio.

.I'm gonna try to help you a little bit:
PARA- indicates the purpose of the action. Example:
Él trabaja para ganar dinero (He works to earn money) → Why does he work? He works to earn money.
-PARA can be used to indicate who receives the action. Example:
Yo cocino para Elena (I cook for Elena) → To whom do I cook? To Elena.
-PARA indicates the utility of something, example:
El bolígrafo para escribir ( The pen to write ) → What's the utility of the pen? It writes.

A - It introduces the direct object (What+verb)
In this case is important to know that this only introduces objects, people and sometimes animals.
Example:
Yo busco a Carmen (I'm looking for Carmen ) → what am I looking for? I am looking for Carmen.

-A also introduces the indirect object (Verb+to whom)
Example:
Yo doy una carta a mi padre (I give a letter to my father) → I am giving the letter to whom? To my father.
A- It indicates the purpose of an action.
Example:
Voy a la playa A tomar el sol (I go to the beach to take the sun) → Why do I go to the beach? To take the sun.
(There's like 14 different uses for "a" so I decided to explain you only three, hope you don't mind)

POR- indicates the places where you are passing through.
Example:
Camino por la calle (I walk on the street) → Where am I walking? On the street.
POR=By
El libro fue escrito por Stephen King (The book was written by Stephen King)
POR→ PORque: Because
→¿POR qué?: Why?