Gimp 2.8.22:
My advice reset to the default window layout and start again: Edit -> Preferences -> Window Management Under Window Positions click on Reset Saved Window Positions to Default Values
Restart Gimp, it will be in 3 windows, use Gimp menu Windows -> Single Window mode
A short video (4 mins) demonstrating that and a bit more: https://www.youtube.com/watch?v=i2sKkA3vqvw might help if you can be bothered.
My advice reset to the default window layout and start again: Edit -> Preferences -> Window Management Under Window Positions click on Reset Saved Window Positions to Default Values
Restart Gimp, it will be in 3 windows, use Gimp menu Windows -> Single Window mode
A short video (4 mins) demonstrating that and a bit more: https://www.youtube.com/watch?v=i2sKkA3vqvw might help if you can be bothered.