1. I have experienced with mail lost. ( correct or not. Use "with" or " of " )<br/><br/>2. The reason i asked you to refund the payment or The reason <u>why</u> i asked you to refund the payment ( Do I need to put " why " here )<br/><br/>3. He feels difficult to get up from sit or sitting ( which one sounds correct?)<br/><br/>4. How is the weather? <u>It</u> is raining. ( it means weather, why can't we use " the weather is raining". )<br/><br/>Thank you very much for your help.