I know it is never nice to get a critical review. However, I do agree with healing4me that, on a positive note, they are lettting you know where they want to see changes and by extending probation they are giving you time to work on it. I would try to follow the comments you have gotten, and if there is someone you can approach when you have a doubt while working on something, maybe you can try to do that as well.

Believe me, I worked for someone that was rarely happy with anything, but also never clear about what he wanted instead- even when we went to him and asked. That is much worse than constructive criticism.

I hope it works out for you!