Yikes. Between minus 4 F in the winter and 95 F in the summer. Whew. That's an interesting climate. Maybe it is comparable to USDA hardiness zone 4b, 5 or 6? Many Bulgarians came to America and settled in the area of Chicago, Illinois.
Hosta, Coleus, Daylily/Hemerocallus, Bearded Iris, Lavender, Phlox, Coral Bells, Salvia, Huechera ....um, what else?
Calycanthus is a shrub which has sweet smelling flowers and does well in the shade. Here is one example:
Ajuga is a good ground-cover plant. One example of Ajuga is the 'Chocolate Chip' which may be sold in your area as Ajuga x tenorii 'Valfredda'.
Astilbe will tolerate your climate.
When I think of a shade garden I think of plants with light colored leaves, variegated or light colored foliage, or light colored blooms.
Hopefully others will chime in with more suggestions.
