Example:
I have problems doing maths
I have difficulties in maths
I find maths difficult.
I find maths hard.
I think maths is difficult to do/understand.
I have troubles with maths.
I have problems understanding this sentence.
I have difficulties understanding this sentence.
I find this sentence difficult to understand.
I find this sentence hard to understand.
I think this sentence is confusing.
I have trouble understanding this sentence.