I ( to suffer ) from fever for three days.

Past perfect tense এ before -  এর পূর্বে past perfect tense এবং before এরপর past indefinite tense ব্যবহৃত হয়।  আর after থাকলে after এর পরে past perfect tense এবং after এর পূর্বে past indefinite tense ব্যবহৃত হয়।

Lest দিয়ে কোন sentence গঠন করা হলে, Should/might + verb - এর মূল form ব্যবহৃত হয়।

The correct word for the blank is suffer. The completed sentence is: "The poor suffer much in winter." 

The correct phrase is "gaining".the correct sentence is: "I went to the library with a view to gaining knowledge."

Lie verb - এর present participle হচ্ছে lying

আমি ভিখারিকে মেঝেতে শোয়া অবস্থায় দেখলাম - I saw the beggar lying on the floor.

The phrase can be completed with the idiom "out and out".The completed sentence reads: "He is out and out a rogue",