I have a gamesave i downloaded from how can i put it into the game

Theoretically, you can do that, if you manually create the folder directory of the savegames that would automatically created by the game. Place it in the right place and name it with the right name, and imho it will work.

See here https://forums.obsidian.net/blog/7/entry-175-location-of-save-games/

 

C:\Users\ --> [Your personal folder] --> Saved Games --> Create "Pillars of Eternity" --> Move save here.