Press Alt + Spacebar again to open the window menu, arrow down to Size, and press Enter . Press the up or down arrow key if you want to resize the window vertically or the left or right arrow key if you want to resize horizontally.
How do I set a window to a specific size?
Resize a Window Using Keyboard in Windows
After that press Alt + Space shortcut keys together on the keyboard to open the window menu. Now, press S. The mouse cursor will turn into a cross with arrows. Then use the left, right, up, and down arrow keys to resize your window.