I'm sure there's a lot more CGI than we can spot. They had to do something to make those impossibly long shots continuous. But there were really only a couple of places where it was obvious. And even then it wasn't bad.
Spoiler!
The only obvious CGI scene to my recollection is when they were walking by the German artillery remains with all the left over shells. The other was I believe the ending where he was slowly walking towards the tree.