Hi there. I might have misread your post - sorry if I have - but if you want to filter the gradebook so you just see your group (class) and not others then - presuming you have set up your groups in the first place then you need to set your assignment or whatever to separate or visible groups. Then at the top of the screen you will get a box with each group/class in and you can choose the one you want to see only. (quick screenshot attached)
