Answer:
Sergei's response (considering his personality and what he hides) is reasonable. In his cultural experience Sergei remained quiet, without great socializing and would like to maintain his privacy.
Step-by-step explanation:
Sergei is a reserved person, who doesn't like to have his space invaded. Although he is in a country where socialization and conversation between people is more common and normal, he has not been involved in this culture and maintains his privacy and distance from social relations between locals.
For this reason, when Yoni suddenly appears and invades Sergei's house, he feels extremely apprehensive and ends up acting totally irrational. Although the way in which Sergei responds to Yoni's invasion has been disastrous, we can consider it reasonable in view of Sergei's personality and what he is hiding.