I have had the unit since this Thursday, but my unit sounds more like a refrigerator with a strong fan noise. I haven't noticed any high frequency sound. Do you mean like certain shop devices or cat scare?

The first hour it had a special smell that quickly disappeared.

Unfortunately, many of these monobloc air conditioners are quite loud in operation, too loud for use in a bedroom, for example. Since compressors and fans are built into the units, they are not always quiet. However, there are models that are somewhat quieter. And 63 dBA is unfortunately already very loud. For quiet operation, I would recommend this model, which is much quieter, with a maximum of 51 dBA in operation, which is really much quieter.

Wood's AC Milan 7K Smart Home (25 m², 7000 BTU/h)

These models, which actually come from Gree (OEM taken over from other manufacturers), are also quieter, although there is also a humming noise that you can hear, but it is quieter (you can't have no humming noise during operation), and the system also has a maximum of 52 dBA:

Daitsu APD9x Mobile Air Conditioner9000 Btuh, R290, A