真

很 is the default word for 'very', and half the time it barely means anything at all. 他很高 sounds like 'he's tall' rather than 'he's extremely tall'. 真 does the opposite job: it shoves you, the speaker, right into the sentence. 真高啊 is a gasp at a tall guy on the subway. 很高 is a line you'd read off a medical form. Quick test: if you'd shrug while saying it, use 很. If you'd raise your eyebrows, use 真.

The 的 is not decoration. 真的 is the all-purpose version you can drop anywhere: 真的吗? 这是真的 他真的走了. Bare 真 is shorter, louder, and usually lives in reactions like 真好 or 真会飞. A one-word 'Really?' is always 真的吗, never 真吗. When you're unsure, keep the 的, because nobody will blink at it. “手机在手中， 飞机真会飞。” (The phone is in your hand, and planes really can fly.) ── [《电脑没脑子》](/read/computers-have-no-brains#s1)

English loves stacking emphasis: 'really very good', 'so totally worth it'. Chinese gives 真 and 很 one shared seat before the adjective, so only one of them can sit down. 真很好 hits native ears the way 'very really good' hits yours. Pick by tone instead: 真好 is a reaction, 很好 is a report. The same pile-up breaks 真很会飞, where you want either 真会飞 or 很会飞.