1863 historic home

I'm restoring an historic stone building as my home. Because the building was previously a restaurant and the interior mortar was sooty, I removed 1/2 inch of the old interior mortar and I'm replacing it with the original blend. (minus portland cement.) On one wall, water from the outside will sometimes seep through the rock because the ground comes to the floor level on that exterior wall. I'm pulling away the dirt on the exterior, but I don't know how to properly waterproof the exterior rock before I replace the soil there. The soil does slope perpendicular to the stone wall because it's on the side of a hill, and not to replace the soil would look weird. Also I place plants in that area as it is next to the steps to the house. Can someone please advise me?

[TJ1962]

Care must be taken with stone foundation during escavation. There may or may not be a footing and most likely no drain tile system. Stone would need to be parge coated, waterproofing membrane and/or drainage board. A backfill of gravel would be good but not good to grow plants.