yes these are really good answers. Congrats !! :)

We're all guilty about it. --> You have actually combined two phrases to make an unnatural one. "We all feel guilty about it" --> Perhaps they have not done anything but feel guilt. "We're all guilty of it" --> They are admitting to doing a bad thing. I have never seen you acting like this before. --> This is grammatically perfect but I think using "act" not "acting" makes it a little more natural. We are in the preparation process for the new season. --> This is grammatically perfect but it seems to wordy because "prepare" is more commonly used as a verb, so the following sounds more natural: "We are preparing for the new season"

"guilty of it" not "guilty about it." Otherwise, great!