In, on, at... Please correct.

Learning a language has many difficulties. For me "in, on and at" is one difficulty. I usually speak in Spanish, and Spaniards have the word "en". This word is the some for a "in, on and at". Can you tell me if I use "in, on and at" well in these sentences?

My friend John is ill, he is at the hospital. => Good
I am in the hospital with John today => Good
The bottle of water is on the table. => Good
We will go to at the cinema tomorrow => Good
You are at your work and your brother is in the garden. => Good

Well, it seems "at" when let's do something, "in" a place and "on" when we refer to a thing on top another thing. But... if I am at the office and my office is in Paris, is it correct to say "I am at my office in Paris"?  => Yes

Thank you.

In, on, at... Please correct.

Learning a language have more difficulties is difficult. For me "in, on and at" is one difficulty. I'm usually speaking in Spanish, the Spaniards we have the word "en". This word is the same for a as "in, on and at". You can Can you tell me if I use "in, on and at" well in these sentences?

My friend John is ill, he is at the hospital. You very often need to use  "at" with an article like "the, a or my" when you're using it to place someone at a physicial location. You could use "in" here too because if he is ill, he is "in" the hospital.
I am in the hospital with John today  "in" is good here but "at" works too.  However "I am on the hospital" means you are on the top of the hospital roof.
The bottle of water is on the table. Perfect
We will go to at the cinema tomorrow You could say "we will be at the cinema tomorrow" but when you use "go to" no "at" is needed.
You are at your work and your brother is in the garden. Perfect

Well, it seem we use "at" when we are doing something, "in" a place and "on" when we refer to a thing top other thing. But... if I am at the office and my office is in Paris, is it correct "I am at my office in Paris"?

Son algunas ejemplos de como creo que las palabras traducir.  Dices me si esos son correctos en espanol.

At-estoy a la casa-I am at the house (Creo que puedes estar en el jardin o en fronte de la casa, pero "estas a la casa")

In-estoy en la casa-I am in the house (Creo que no puedes estar en fronte de la casa, solo en la casa)

On- estoy sobre la casa-I'm on the house.

Under-estoy baja la casa-I'm under the house

Thank you.