Is purchasing a house and complete renovation affordable?

It is now clear that you really want the house. You have indeed saved up a lot of money, but there is a difference between being able to do something and having to do it. There is also the possibility to renovate gradually. The damp basement... does it absolutely have to be done? So do you need it? The roof, windows, electrical system, and water pipes should be finished before moving in. Everything else can be done later. It is a bit annoying, but you can continue with that from ongoing funds. Sometimes you just have to bite the bullet and you can't have everything at once.

If anyone has an alternative, I'd be happy to hear it, I'm really open to suggestions

I would look for an alternative that doesn’t require a complete renovation. The risk is high that it will be more expensive than planned, and living on a construction site is no fun. Maybe you will find a property that is habitable in its current condition. Not quite as old. Something from 1990-2000.

The market is tipping back in favor of buyers, and you have good conditions compared to many other interested parties, since you have good savings performance and a lot of equity.

Unfortunately, this is all quite nonsense. Dieter Nuhr put it nicely... "The additional years you get from healthy eating, sports, etc... you don't get them now... you get them at the end, when you are old, frail, and demented..."

Therefore, the "60 and cancer" thing is complete nonsense. Cancer is primarily a disease of old age. The biggest risk of getting cancer is that you grow old. The older you get, the higher the risk.
The individual case has no relevance for statistics...

Just as a note. A 50-year-old man has about an 85% chance of reaching the retirement age of 67 alive.

Well... for the reasonably decent properties that don't need a complete renovation right away, prices aren't currently falling nearly as much as for the urgent renovation cases. A house from the 90s is also not fantastically insulated; we're still talking about 150 kWh/m²/a. And you all fundamentally advise against simply replacing an old gas heating system with a new one. So even with houses from the 90s, you hardly get by without renovation before moving in. Once you live there, you don't clear out all the furniture and install underfloor heating with a heat pump after five years. And a heat pump automatically also requires the energetic renovation of the facade and windows...

Apart from that, houses built between 1990 and 2000 are also 23-33 years old. They are usually quite worn because many people do rather little to their houses over their lifetime...

I completely agree with Schorsch. You are 28 and honestly don’t really know where your journey is going. Children yes? Children no? How many? It doesn’t make sense for you to buy a big house now with a lot of money at record interest rates... and then realize in a few years that you actually don’t want children... or that it doesn't work out... that can also happen. I know more than one couple who wanted to wait to have children until the perfect moment seemed to come... and then it didn’t work out.

Well... with the somewhat reasonable properties that don’t need a complete renovation right away, prices currently don’t fall nearly as much as with the urgent renovation cases.

Sure, but then you also don’t have to invest that much after the purchase.

In that respect, you rarely get away without renovating houses from the 90s before moving in.

That is nonsense. It depends on your own standards and the property in question.

Once you’re living in it, you don’t take out all the furniture and install underfloor heating with a heat pump after 5 years. And a heat pump automatically requires an energetic renovation of the facade and windows as well...

That is nonsense as well. You can run a heat pump easily without surface heating. Existing radiators can be replaced with suitable ones if needed. The heating works even without energetic renovation – you just consume more energy. My sister has been running an air-to-water heat pump in an old, unrenovated house for over 2 years now. They have only replaced a handful of radiators so far. The rest of the renovation is still pending. Yet they heat their house in winter without any problems. In terms of cost, it’s already somewhat cheaper than heating with oil before.
In combination with photovoltaics, it’s even cheaper. And yes, we all know that there is not much solar power in winter from photovoltaics. But there is in spring and autumn. Germany has a long heating season; the synergy exists, even though heat pump opponents like to deny it.

Besides, houses built 1990-2000 are also 23-33 years old. That is usually pretty worn out because many people do rather little to their houses over their lifetime...

Not every house is worn out just because it’s 25 years old. It depends on the previous owners, the materials, how it was treated. You can’t generalize. You don’t have to buy a poorly maintained house. Or you factor that into the price negotiation. It’s not a deal-breaker.

I’m totally with Schorsch on this. You’re 28 and honestly don’t really know where your journey is headed.

That is no reason to keep wasting money on rent if you would like to live in your own home.

Record interest rates

Every time you drop a bomb like that, you risk some boomer choking on their coffee from laughing. You have to live with that conscience.

... or that it just doesn’t work out... that can happen too. I don’t just know one couple who kept waiting to have kids until the perfect moment seemed to have come... and then it didn’t work out.

Assuming as a young couple without other evidence of infertility and therefore not buying a house would be extremely pessimistic.
Depending on what you count in, infertility rates lie between 8-10% or even below. And many of those can be helped with IVF. Infertility that cannot be overcome with today’s medical help is a fate that (fortunately) only a small percentage of couples suffer.

There, the wish is the father of thought. Heat pump without underfloor heating? Have fun. Don’t read so many advertising brochures ;)

Based on the current price level, we actually have record interest rates. If the boomer chokes on that, he doesn’t deserve better due to lack of education. Darwin Award is a term?