Hi. Usually babies start sleeping well at night from 3 months . But some babies take a bit longer , up to 6 months to achieve this . Make a regular schedule for sleeping . Feeding him more before sleep so that he does not wake up hungry ...also make sure the bed is comfortable and no disturbances.. at night when he wakes up keep the lights and noise low and don't spend too much time talking to . He should figure out  night time is for sleeping... Interact and play with him well at day time .Keep house bright and well lit on the day ... Don't try to minimize regular day time noises like phone or music or dishwasher..