if i get indian visa, and i want to see schengen country before moving to India,tell me how to get 3days transit visa to one of schengen country , with hotel reservation and which country is good for me to do

i want to travel to another country eastern europe , i have an invitation letter but their embassy is not our country , how can i do it.

He is from Nigeria.

please i want to know the documents that i will produce for my friend that want to visit me in Italy.