Farmhouse with groundwater problem - How to best approach it?

Hello everyone

We have bought a 70-year-old farmhouse, which of course still needs quite a bit of work, but we are aware of that. I am a trained carpenter and want to do as much of the work on the house myself as possible.

Now to my question: the house is located in East Frisia and we have three rooms in the house that are hollow under the wooden floor. So underneath there are beams and then earth, and in one of the three rooms (kitchen) groundwater sometimes comes through.
Now I would quite like to compact and fill these rooms; what is the best approach for that?
I have read a bit on the internet but didn’t really get much wiser from it, hope someone has experience with this. The second consideration was to have a company do it, but I think that will definitely be much more expensive.
Maybe someone can help me, thanks in advance for the answers.

If you want to do it right, it will be a huge effort...

My brother renovated an old farmhouse from the 16th century and also had to completely redo the entire floor (though they only had cold feet, not wet ones...)

Does the earth start directly under the wooden floor? So no insulation at all? Like in a barn? You live in there??? phew...

So if you want a floor that at least somewhat meets today's standards for comfort and energy regulations, then the old floor has to come out completely, dig at least 50cm deep into the ground, and then, if I remember correctly, gravel is laid, insulation, concrete slab, floor construction (screed, wooden floor, possibly both)

Are the walls dry, since the house is practically standing in water?

If you no longer really have a house but a construction site, then I would also consider drying out the walls.

And last but not least: the house is only 70 years old? Is it already under monument protection? I hope not for your sake... Still the question: is it really worth preserving? When I read that there is practically no decent floor, I would seriously consider whether it makes sense to throw a lot of money into maintaining a home that at least approximates today's requirements or whether it would be better to think about demolition and new construction.

We bought a 70-year-old farmhouse, [...] and we have three rooms in the house that are hollow under the wooden floor. So underneath are beams and then comes earth

The building description doesn’t sound like it is even seventy years old - that would have been “post-war” even. And it sounds as if only three rooms are affected, and other rooms have a differently constructed / founded floor (?)

A possible solution is a pump that activates at a defined groundwater level. The water then goes into the sewage system.

Of course, I cannot say what damage the house already has and what still needs to be done.