The trick is to do a Ctrl, Alt and right-click anywhere in the window of the program you want to resize, a right-click on the top window bar or a single click on the blue button top-left ..... which will open a new menu including options for "Window Size" as well as "Remember" to keep the settings for a next time.
We have a tutorial (in English) that has some pointers on how to handle E16 which might be helpful too:
https://forum.elivelinux.org/t/tutorial-on-handling-e16-by-customizing-the-desktop
