Translation:The stairs are next to the bedroom.
Yes. In my speech community we may also say "the stair", meaning the staircase, and it is singular and should be accepted. We should not be forced to say "the stairs are" when the Greek is singular. This raises the question what the Greek, "οι σκάλες", means. In English each "step" is a "stair" and all the stairs make a 'flight of stairs' or staircase. "Stair", meaning flight of stairs may sound a little archaic, but it is not wrong. "There is a single stair giving access to the library" does not mean a single step, but a single flight of stairs.
It is the same in Spanish (la escalera, las escaleras) and Italian (la scala, le scale). 'Σκάλα' is apparently a Latin import to Greek. But to be fair, there are many discussions of, and much disagreement about, the proper use of these singular and plural forms, and the Spanish and Italian translations include the English 'ladder'. So it can be a confusing subject. But in general, across languages, 'stair' and 'stairs' are used indiscriminately.
Δίπλα στην for feminine nouns, Δίπλα στο for neuter.
Feminine exp. (κουζίνα is feminine)
- Το σαλόνι είναι δίπλα στην κουζίνα - The living room is next to the kitchen.
Neuter exp. (σαλόνι is neuter)
- Η κουζίνα είναι δίπλα στο σαλόνι - The kitchen is next to the living room.
I hope this helped. ^.^