1. If you do it at all, do it well.
(What is the meaning of 'at all' here?)
2. Do you believe it at all?
(What is the meaning of 'at all' here?)
3. I don't know him at all.
(What is the meaning of 'at all' here?)
Greetings
1/ at all in that context means if you decide you will go ahead then do it well . It means it may or may not happen but this what you should do if you decide to go ahead ....
2/ This form of "at all" means totally or completely . It applies that some of whats being said may be true or none of it . So the person is being asked if they believe anything of what they have heard
3/ This 'at all"one is a denial or uncertainty . Either the person should know 'him' or they are denying knowledge when they do know him . eg everyone knows Michael Jackson but you don't and people ask you about him and you could say "Sorry i cant tell you my opinion I don't know him at all"
Hope this helps .
Mr McAlpin