Because Italian uses the verb avere (to have) here, just like English does in I have a good impression.
So Ho una buona impressione is literally I have a good impression.
You would not normally say sono una buona impressione, because that would mean I am a good impression, which does not make sense.
In Italian, adjectives can come before or after the noun, depending on the adjective and the nuance.
With common adjectives like buono, putting the adjective before the noun is very normal:
This sounds natural and standard.
In many cases, adjective position can slightly affect style or emphasis, but here buona impressione is just the usual expression.
Yes. Very often you will add di to say who or what your impression concerns.
Examples:
Notice that di + il becomes del.
So the full pattern is often:
Ho una buona impressione di + person/thing
On its own, Ho una buona impressione is grammatical, but in real conversation Italians often specify the person or thing:
If you say only Ho una buona impressione, it can still work when the context is already clear.
For example, after meeting someone, if everyone knows who you are talking about, this shorter sentence is fine.
No. They are related, but they do not mean the same thing.
Examples:
So one is about your opinion, and the other is about the effect someone creates.
A simple pronunciation guide is:
oh OO-nah BWOH-nah eem-prehs-SYOH-neh
A few helpful points:
If you want to sound more natural, keep the sentence flowing smoothly:
Ho una buona impressione.
Yes, and it is very common, but it means the idea from a slightly different angle.
So:
Both are natural, but they are structured differently.
Usually, yes. Buona impressione is the standard and most natural translation in many cases.
Examples:
Italian can sometimes use other expressions depending on context, but buona impressione is the normal phrase to learn first.