Leave a gap between the concrete and the siding, so that the water can run away/evaporate before it reaches the wood. Also make sure that the water flows away from the siding when it rains, and not up against it.
There should be a small slope away from the siding, so the water is not retained there, but leads away to avoid further damage to the siding/construction.
In Norway where I live, all houses have a clearing of 2-3 cm at least between the concrete and wood, and the floor is made so the water runs away from the building to avoid exactly this issue, because of the amount of rain and sometimes melted snow during the seasons. It’s part of the building code for houses.
Best of luck to you in getting this sorted out, make sure you get all the damaged parts out, so you avoid secret problems later on.