The great escape quest

[Lachs]

On the great escape main quest; there is a big bug, you should jump into the well and should be able to run in those ruins, but in my case these ruins underneath oxenfurt are completly flooded, which means i can't break the wall with aard, cause you can't do spells under water ..... there is another cave on the southern side of the map from novigrad (there is a quest where you should find some people in this mine but dont know the quest name) anyways this mine is flooded aswell, so my question is ... how do i get rid of this water? how can i fix this? why is there water where no water should be?

i tried some mods, didnt worked, tried to reinstall the complete game, didnt work, .... i have no idea how i should be able to do the main quest any further ....