I have reduced my GPU temperature from ~83° to 60-65° by doing two things: first, I reduced the quality of the viewport picture by going to Settings → Engine Scalability Settings and setting it to “low”; second, I limited the FPS, which doesn’t need to be high while I’m learning new stuff, to the lowest possible 15 FPS by going to Edit → Project Settings → searching for the term “frame rate” → setting a fixed FPS rate under the “Engine - General Settings” group.