In epistemology & ontology "Realität" relates to what we perceive as our environment - objects, sounds,.... So a optical illusion would be not real in sense of "Wirklichkeit", its not a real existing part/object of the universe, but perceived and constructed from a constructivism point of view. So it belongs to our personal constructed "Realität"
In english "Wirklichkeit" is translated to actuality, objectivity, substantiality, realness, reality, truth, etc. How should these words be translated into the terms of English-language technical philosophical discourse?