I got this cherry tree sapling in the spring this year. I have basically just been letting it grow and establish its roots in the new pot. I had a bit of problems with insects, which is why I think some of the leaves don't look quite as good.

I am pretty new to bonsai, this is the first one that I am trying to "start" myself. My other one was purchased from Costco. I am wondering how far back I am able to prune the tree, I think it may be a bit too tall, but I don't want to trim it too far back, and accidentally kill the whole tree. Any suggestions would be appreciated, thanks!!!

At this time of the year you cannot cut as much as you can in late winter and early spring.

I would not cut at all until the trunk has thicken considerably.