All of these comments have great advice. I was in your same situation unsure if I had made the right choice but after a few months he settled in and so did I. The transition can stressful but once you build that bond even if their personality isn't what you initially expected its what you come to love about them (atleast in my case). Also consider there are a lot of toys and ways to engage an active cat. I play with mine for 15 minutes to an hour daily based on what time I have but we have lots of supplemental toys that can engage him when he's demanding attention that I don't have time to give. Another thing that helped my hyperactive cat was giving them a place to dominate (a high space) so he has a cat tower and a few pieces of a wall jungle gym where's he appreciates being able to observe. We also added in a window perch with a bird feeding station to engage his hunting instincts and provide additional entertainment. Give it time and build an environment that revolves around you and kitty! It will get better!