Complex sentence: After his death, an alien comes to earth and learns about shaani and disguises itself like him and seeks revenge with land-lord in the meantime falling in love with the real shaani's love interest.
Split into simpler sentences: After his death, an alien comes to earth. When that alien learns about shaani, it disguises itself like him and seeks revenge with the land-lord and in the meantime falling in love with the real shaani's love interest.