To find the sword named Brokvar pick up the key to the cellar from one of the rooms inside the house:

Pick up theket to the cellar tp find the sword named Brokvar in Possession in Witcher 3 Wild Hunt.

Then open the trapdoor at the back right corner of the house, go down and pick up the sword named Brokvar:

Go down into the cellar to find the sword named Brokvar in Possession in Witcher 3 Wild Hunt.