Mojave doesn't remember window position/size for a specific application? Normally on Mojave all applications windows settings are stored automatically.
Still I have one program which does not do this, every time I re-open this app I have to maximize (not full screen) it's window all over again.

Is there any way I can achieve this automatically?
Making that the program will remember windows size and position after closing an reopening?
Maybe a plist file, terminal command, automator, or third party application which does this automatically?

Many THANKS for all your help.
Here is the list of solutions:

Open a Finder window, hold down the option key and resize the window as you wish. Close all Finder windows and next time you open a new one it will remember the size.

Meanwhile, you can use an app like Stay to remember and automatically reset the position of any window. 

You might also look at window managers such as Magnet that allow easy manipulation of windows.