Hola Nico. Tal como te dijo Gary es un poco complicado, porque tiene muuuuucha excepciones, pero una forma de clarificar un poco las diferencias sería: 1. In= Dentro de o rodeado de o por. 2. On= Sobre, hablando de una superficie, por ejemplo: On the top of the mountain. 3. At= Cercano a, por ejemplo: "I'm at the door", se supone que estoy frente a una puerta, o sea estoy en la puerta, no sobre ella, no dentro de la puerta, pero aún así estoy "en la puerta".

It is really complicated to use them correctly. You need to learn which ones go with which situation. Sometimes you can only use one of them, sometimes you can use two. Sometimes those two words have different meanings. GENERALLY - on means on top of something, in means surrounded by something, and at means beside or around it. e.g. you sit in a chair, on a stool, and at the table. BUT - that is the general idea, and there are lots of exceptions. e.g. you ride in a car, but on a bus or train. You can be on the road, but at the corner.... I suggest you find a book, or an online resource and start learning them, and then practise them.

Qué quieres saber ?

Hola, me parece que hay que leer algo y trabalhar sobre esse. https://en.wikisource.org/wiki/Category:Short_stories ciao