If it's any consolation, Grieg himself was no expert at his own Concerto. He regarded Percy Grainger as being the best around, and observed that if he, Grieg, could play his own Concerto properly, then the way Grainger did it was the way he would have chosen. I don't suppose I have the words exactly right, but you get the general drift.
Grainger made piano rolls of the Concerto, and it's possible to accompany them with a live orchestra, but they were originally issued for domestic use, with an orchestral piano part added, and he takes great liberties with the tempi, which makes it very difficult for the poor conductor!
Oh, and by the way. Grieg's family came originally from Scotland, and the name was therefore Greig, as in David Greig, the provision merchants that those over fifty may remember in Britain. So his ancestry must take part of the blame for the fact that his name is so often misspelt!