Purchase decision small semi-detached house 100 sqm from 1930

What relevance does this have to this topic? The question is serious and not annoyed.

Well, whether switching to a heat pump makes sense or is basically feasible. If you operate with 50 degrees supply temperature, it would already be very borderline. But for that, all numbers/expenses would be needed. Hybrid definitely doesn't make sense. It would be hot water in summer "free from the roof" via photovoltaic/air-water heat pump and then heating with gas in winter. Over 80% of the energy demand still from gas. In total, nothing saved, on the contrary, higher expenses than now.

Topic heating: Does it make sense to initially continue operating the heating with low temperature radiators and underfloor heating in conjunction with the oil heating, then with a lower flow temperature – and then simply replace the oil heating later with a heat pump? Or to put it another way, is that even possible?

Currently, it is difficult to get a heat pump at all. The idea would be to simply replace the oil heating with it later, once the market has calmed down again.

I want to bring this question up again. If anyone has an opinion on this, please share.

Technically, this does not pose a problem.

I want to bring up this question again. If anyone has an opinion on this, please share.

I am just an amateur, but in my opinion, it should be possible. However, I would advise consulting the plumbing company, which could ideally also carry out the replacement if necessary.

Well, whether switching to a heat pump makes sense or is basically feasible. If you are running with 50 degrees flow temperature, it would be very borderline. But you would need all the numbers/outputs for that. Hybrid definitely makes no sense. That would mean hot water in summer "free from the roof" via photovoltaics/air-water heat pump and heating with gas in winter. Still over 80% of the energy demand with gas. In total, nothing saved, on the contrary, higher expenses than now.

I don't have the numbers handy now, but the heating was always running at around 42-44° in February. Overall, as far as I have read and been advised, it is technically possible and reasonable to switch. Our plumber, however, says that it makes no economic sense because the gas heating would still run well for many years.

that it does not make economic sense because the gas heating would still work well for many years

An old Daimler that consumes 20 liters of premium fuel per 100 km will also still function well for many years….therefore the question(s) about the current (future) total costs… (Although in your case, the consumption is not particularly high, but the kWh is/will be expensive…)