Where to learn GTK from?
 

all spam

GTK has extensive documentation on its website. https://docs.gtk.org/gtk4

In addition, GTK comes with gtk4-demo that illustrates how to use the widgets.
Ed

I cordially recommend that you download the Gnome source code, or the source code and documentation for any number of other projects which might today be found on GitHub and SourceForge.

I would look into employement opportunities FIRST unless you are a hollywood star's kid and donating free gaming to linux (which I'll applaud!)

I think your linux distro has "documentation packages" and "developer packages" for GTK which should have everything.

xlfs-0.2 - I can think of multiple cases when I needed to solve a problem; finding the solution required writing software; and the software benefited from having a GUI.

GUI programming is more useful than you think.
Ed

To embark on mastering GTK (GIMP Toolkit) for GNOME development, one can initiate the journey by delving into the official GTK documentation alongside online tutorials. Additionally, immersing oneself in GTK programming literature and actively participating in the vibrant GTK community can provide invaluable insights and guidance. Through consistent practice with GTK widgets, one can steadily cultivate proficiency in this domain, laying a strong foundation for future development endeavors. Incorporating these strategies into the elp with research proposal[/URL] can elucidate the meticulous approach towards skill acquisition and project preparation, fostering a comprehensive understanding of the proposed study's methodology and objectives.