It sounds to be like whatever you downloaded contained a virus or just messed up your game.
Try going into your computer via Computer -> OS(C:) -> FeralHeart and delete the WHOLE thing so that there are no files left. When you uninstall the game, it doesn't necessarily remove the files that are corrupted so you'll have to do it manually instead.
Now that ALL your FH folders and files have been removed, you'll have to start from scratch and once again download the game. This won't effect your characters and the like, it'll just mean that you'll lose all your maps, presets, custom textures etc. Save the ones that you trust in a different folder to be extracted back into their original files once you've redownloaded the game.
