I am a 72 year old senior and have recently switched from Ubuntu, having been a user since Breezy Badger.
The reason for my change to linux lite was that Ubuntu has become increasingly bloated and unwieldy. My oldish Laptop is an Acer Aspire 2core pentium processor and 8G ram.
I am very pleased with the switch but have encountered two slight problems;
1) the main one, is that Gimp opens in a window that is too large for the screen
2) the second of less importance, is that stellarium only opens briefly then closes again. I can run this on another machine so it is not such a problem.
I am happy with using the command line, but, having experienced lots of problems with Ubuntu 20.04, I am reluctant to mess, (without advice), with an otherwise perfect system for my purposes.
I would appreciate some assistance as Gimp is my preferred photo editor.
Thanks in anticipation
Error: O.S. is Linux lite 5.0 not 6

Right click on the bar at the top of program that is too big for your screen, & choose 'maximise' - you'll find it then fits.

For a program that tries to start but disappears, try running it from the command line, it will likely indicate that something that it relies on is missing - install the missing program.

Thanks for the quick response
The Window is too tall and is not resolved with the usual options(- my guess is that the screen ratio is 4:3 and not the laptop ratio), but I have no Idea how to alter this. Right click on the top bar does nothing.

Thanks for the tip if running stellarium from CLI I think I can sort that now. The video driver needs up grading.