What's the difference between en and eng in pinyin

What's the difference between en and eng in pinyin

The first is the front nasal, the second is the back nasal

I can't distinguish between an and ang, en and Eng. what's the difference between fan and Fang, Shen and Sheng?
Would you please tell me more about the shape of your mouth (the position of your tongue, etc.)? I'm from the south. I can't distinguish the pronunciation of this kind of sounds. Don't tell me what Pinyin wall chart to buy? I want ready-made answers

To put it simply, when making an an sound, the tongue stretches forward to the lower teeth, mainly at the throat
When making ang sound, the tongue sinks and touches the lower gum in the mouth, mainly the nose
Rice, in pronunciation, the tongue and the lower teeth and the lower lip contact each other
In pronunciation, the tongue is touching the mouth. In pronunciation, the tongue only needs to be upturned, not touching the mouth

AI, EI, UI, Ao, ou, IU, ie, UE, er, an, en, in, UN, ang, Eng, ing, ong how to pronounce these Pinyin with one Chinese character
Hurry!

AI, AI, Wei, Ao, ou, you, Yu, Yue, er, an, en, Yin, Yun, Ge, Ying, Nong (this word is not accurate)