Possible house purchase - air-water heat pump possibly a money pit

Hello experts.

A house, which was massively built three years ago (without insulation), is being offered for sale.
The house has an air-to-water heat pump, as well as a fireplace. There is neither a solar nor a photovoltaic system.
Heating is done with the air heat pump and fireplace, the energy certificate is available. It has been rather fluctuating over the three years, but well.

The seller gave me the invoice for the heat pump and underfloor heating yesterday.

How can I tell whether this is a "good" energetic concept?
Before I buy, I want to rule out that I am getting myself a money pit here.

Do I possibly need the exact exterior wall thickness (which type of brick) and roof insulation and window values etc. for this?

I would be happy to receive some information. Have a nice evening and best regards. Chris

How high is the electricity bill? How many people live there? Karsten

How can an energy certificate fluctuate?

Ps. Electricity consumption does not necessarily say much about the heating consumption! Especially if the fireplace was in continuous operation. Or if the owners set it to a maximum of 20 degrees.

The house is currently no longer inhabited. The couple who built the house separated two months ago. Energy consumption for electricity is 24000kWh, for wood 15000kWh, all given for three years.
Thank you for your feedback.

Let's leave out the wood for now, I have no idea what 5000 kwh per year of wood costs. Electricity is 8000 per year. Two people, my wife and I, need 2000 per year without the pump for cooking, washing, and so on. That's roughly 800 euros. So that would be heating costs of 2400 euros per year at our electricity price. Plus wood. Not exactly cheap. Or am I making a calculation error here? Karsten

The energy values within the three years have been very fluctuating according to the seller.