How to search the mail I need from many email fast?

Select "Search" on the left side of the page,and enter keywords or search type and folder.Click "Start to search",and you can find the email you need easily.

Can I restore the emails I delete previous?

Sorry.Now we only provide complete match content search. If you click "Delete" to delete an email, you can find the delete ones in "Deleted" and move them to inbox or personal folder.