Damp basement built in 1962 external sealing / drainage?

Hello everyone,
we have undertaken a complete renovation of a house built in 1962. One question mark is the moisture in the unusual basement.
Can it be estimated from the following pictures what needs to be done to get the moisture under control? With the high temperatures right now, I usually have 75-80% relative humidity. Seal from the outside? Additional drainage? Other options?

Many thanks for your help and tips in advance.
Benny

Hard to say. Dig it up and seal it from the outside? Are these all exterior walls? Is there also such a nice fluff on interior walls?

My basement is currently damp as well. Just like with you, it's due to the humidity. But otherwise, my basement is completely sealed from the outside.

Therefore, I would have someone come take a look.

Yes, mostly only exterior walls are affected. It "draws" about a meter into an adjacent interior wall. Especially when it has rained, I think it gets worse. But maybe also because of the increased humidity then(?)
Who is most likely to be able to say something about this? Mason?