I learned how can I use the widget shortcut plugins for edit the block in the page of GrneratePress, but I don’t know how I can adjust image size so please let me know about that as below link; now too small size..
To clarify: Do you intend to display multiple images on the sidebar widget area? if not, perhaps the Image widget will serve you better than the Gallery Widget.
Upon using Image widget, you should be able to see an “Edit Image” button.
A popup window of settings should popup. You should be able to see a dropdown for sizes.