Landscape problem need fix ASAP!

i don’t know wth is happening lately but my landscape is hecking with me like this
1- its blocky ( like minecraft )
2- collusion is broken
3- everything else
if you look at the second picture you will notice that the landscape i made is smooth but in unreal it goes full stupid on me… any help? ( LEARNED WORLD MACHINE HOPING TO FIX THIS HECKING THING!.)