Hard to switch from vi

[Wen Weng]

Hi, I am a vi user for years and am now trying emacs.
I find it hard to get efficient. Can someone teach me some
commands?

1. In vi, to delete a line, I do, "dd" and to delete 5 lines, I do 
"5dd". In emacs, how do I delete a complete line? C-k only delete
from cursor to the end of line. Adding a C-a is really too much work.

2. Is there a repeat last command command like the dot command in vi?

3. In vi, to find a pairing brace I use the "%" command, is there a
command like thins in emacs?

4. Should I really need to switch to emacs?

Thanks
Wen