Accept offer for 16kwp photovoltaic at this time?

If you have a good feeling about him and maybe a few good references, then why not.

But just stupidly asked... what can he do, let's say, worse or better than other solar installers?

What does PVGIS say is to be expected?

Calculate roughly e.g.:

17kw x 1000kWh/a (according to PVGIS) x 0.075 (feed-in tariff roughly) x 20 years (calculated service life) =

25,500

You get that back with full feed-in. Provided you also reach the yield with full occupancy. Meaning you are slightly in the red.
You will compensate that effect through self-consumption. With an air-water heat pump and electric car, you will definitely end up with a plus in the end.
If everything is really included, it’s certainly not a super bargain but the prices are just like that now. If you read through offers in another forum, many are currently even significantly more expensive.
A comparison with an offer three times the size makes no sense.
Prices also often vary regionally.

Do you have other offers? What are they like?

But the heat pump runs especially in winter, when there is no photovoltaic power for self-consumption. From November to February.....

But the heat pump runs especially in winter

[*]Heat demand 6000 kWh/year / 2.8 = electricity demand 2143 kWh/year [*]2143 / 150 days = 14 kWh/day [*]My December yield 378 kWh / 23 days = 16.4 kWh/day would roughly fit, but [*]16.4 kWh / 40 kWp (mine) * 17 kWp (yours) = 7 kWh/day