1. have difficulty (in) doing something
（最正式且通用的表达）
例句：
I have difficulty (in) understanding his accent.
（他的口音让我理解起来有困难）
She had difficulty solving the math problem.
2. have trouble (with) doing something
（口语更常用，"trouble"替换"difficulty"）
例句：
Do you have trouble falling asleep?
（你入睡有困难吗？）
He has trouble with pronunciation.
3. struggle with something / struggle to do something
（强调“努力尝试但仍有困难”）
例句：
Many students struggle with writing essays.
She struggled to finish the marathon.
4. find it hard/difficult to do something
（强调主观感受，较委婉）
例句：
I find it hard to concentrate in noisy places.
They found it difficult to adapt to the new rules.
5. It's hard/challenging for someone to do something
（客观描述某事有难度）
例句：
It's hard for me to learn Chinese characters.
This puzzle is challenging for beginners.
其他替换表达：
can't seem to...（委婉表达尝试失败）
I can't seem to figure out this problem.
not good at...（不擅长某事）
He's not good at public speaking.
注意语法细节：
`have difficulty/trouble` 后接动名词（doing），而非不定式（to do）。
`struggle to do` 后接不定式（to do）。
根据语境和困难程度选择合适的表达即可！
