The sentence "La puerta esta al lado una la ventana" has a couple of grammatical errors. The correct version should be: "La puerta está al lado de la ventana."
Here's the breakdown of the corrections:
- "está" should have an accent mark over the 'a' to indicate the correct tense (present).
- You need "de" before "la ventana" to indicate proximity or location.
So, the corrected sentence translates to "The door is next to the window."