Hello Firro !
Answer your question isn't easy, you must use those words in a sentence to understand the difference between them.
"POR" has different meanings and uses depending on the context. For example:
1) to express gratitude or apology = Gracias por la ayuda.
(Thanks for the help.)
2 ) for multiplication and division = Dos por dos son cuatro.
(Two times two equals four.)
3 ) for velocity, frequency and proportion = Voy al restaurante cinco veces por semana.
(I go to the restaurant five times per week.)
4 ) meaning "through," "along," "by" or "in the area of" = Paseamos por el parque.
(We walk through the park.)
5 ) to mean "on behalf of," or "in favor of," = No voté por nadie.
(I didn't vote for anyone.)
6 ) to express a length of time = Yo estudié por dos horas.
(I studied for two hours.)
7 ) for means of communication or transportation = Prefiero viajar por tren y hablar por teléfono.
(I prefer to travel by train and speak by phone.)
8 ) to show the reason for an errand (with: ir, venir, pasar, mandar, volver, and preguntar) = Paso por ti a las ocho.
(I'll come by for you at eight o'clock.)
9 ) when followed by an infinitive, to express an action that remains to be completed, use por + infinitive = Ella está por cocinar la cena.
10 ) to express cause or reason = El hombre murió por falta de agua.
( The man died for lack of water.)