We arranged to meet in the library.
CORRECT
I've been studying hard so I expect passing the exam.
I've been studying hard so I expect TO PASS the exam.
Please promisse not to cheat again!
CORRECT
have you ever considered to study another language?
have you ever considered STUDYING another language?
My friends appeared finding the exam easy.
My friends appeared TO FIND the exam easy.
I was happy because I managed passing the exam with 90%.
I was happy because I managed TO PASS the exam with 90%.
She suggested to study together that evening.
She suggested STUDYING together that evening.
You risk to fail if you don't start studying now.
You risk FAILING if you don't start studying now.