Need help with some phrases and words in English!

The kitchen is to the left of the bathroom. - more specific position.

"Please read that paragraph at the top of the page."


"I accidentally met James in the street."

"There is a bag full of stones at the bottom of the well".

In most cases your original sentence was perfect.

Best wishes

Bob

Need help with some phrases and words in English!

Both work fine, IMO, but "for the next" feels a bit more common and natural, though.

"The bathroom is on the left / to the theft, and the kitchen is at the end of the corridor."
Should I say "on the left" or "to the left"
Please give me clear examples of when to use one and the other.

"On the left" means you're going down a hallway and the bathroom is a door on the left side of it. You can make it more specific by saying "The bathroom is the second door on the left..." 

I'm not 100% sure about this one... "to the left" is a bit more general and may not be talking about being in a hallway. "The bathroom is down the hall to your left," for example. But in most cases "on" or "to" are interchangeable. 

An even more "native" way would be to say "to your left" or "on your left". Those are 

"Please read that paragraph on top of the page."
Should I say "on top of"?

No. "at the top of the page" is better. On top of gives the idea of something physically on the object, like "there is a frog on top of the page."

"I accidentally met James in the street."
Should I say "in"?

I feel both "on" and "in" could be used, but "on" sounds better to me, but that could be a regional thing. Maybe in England they use the other?

"There is a bag full of stones at the bottom of the well".
Should I say "at the bottom"?

Yep. Sounds perfect.

Need help with some phrases and words in English!

Both are correct

"The bathroom is on the left / to the theft, and the kitchen is at the end of the corridor."
Should I say "on the left" or "to the left"

Both are correct again, but this last sentence would make best sense if you were there to point the direction to the person (To the left according to what?)

Please give me clear examples of when to use one and the other.

"Please read that paragraph on top of the page."
Should I say "on top of"?

"On top of" isn't correct, it denotes something positioned over the page

"Please read that paragraph at the beginning  of the page." 

would work better

"I accidentally met James in the street."
Should I say "in"?

Yes, you could also say "on the street"

"There is a bag full of stones at the bottom of the well".
Should I say "at the bottom"?

Yes, that's correct too