According to my understanding:

• two orthogonal forces aren't related and two orthogonal vectors don't affect each other
• the force of static friction Fs depends on the gravitational force Fg, so Fs = -Fgc = -mg*c (c being the static friction coefficient)

If these two are correct, how can the force of static friction, determined by a force normal to the surface, be directed tangential to the surface and orthogonal to the normal gravitational force?