My kid is 8 months old and he still doesn't sleep all night and he doesn't nap in the afternoon is there anything i can change that!

Bedtime routine: A very common cause of this is routinely rocking/singing/holding child until they are asleep and then putting them in their crib. They have not learned how to "self-soothe." start putting child to bed sleepy but awake, so he falls asleep in the crib without you right there. (you can be close, just make sure he can't see you.) that is a good start.