Quick answer
g, k and h are made at the back of the mouth. g is soft, k has a puff of air, h is a light throat sound.
g
k
h
Hear each sound, then repeat it aloud.
When to use it
Feel the back of your tongue rise toward the soft part of the roof of your mouth.
Common mistake
Mandarin h is lighter than the hard English ‘k’ or a heavy throat sound — keep it gentle.
Practise aloud
高 tall
看 to look
好 good
You’ve got this!
Say the three sounds in a row and notice where they are made — all at the back of the mouth. Then try one in a word like hǎo (good).