Toughest part of learning another language's grammar?

For me, it's been the way that Chinese structures it's sentences in a seemingly opposite way to English. For example,

"I don't feel like eating anything."
"什么东西都不想吃。" (lit: what things all don't think of eating)

Question

Toughest part of learning another language's grammar?

For me, it's been the way that Chinese structures it's sentences in a seemingly opposite way to English. For example,

"I don't feel like eating anything."
"什么东西都不想吃。" (lit: what things all don't think of eating)

Answer

⋯都 emphasizes the object
We can also say: 我不想吃任何东西