Yeah when you are changing the options or preferences for an item it's gives an option of choosing "my time". What exactly does this mean and what is the best thing to set it as.

I am using using a nexus 4 (android) and it is on a wifi connection if that helps

Please could anybody reply quickly as the auction ends soon

Sniping is bidding on last seconds.
The "My Time" value is how many seconds before auction ends.
The default value 5 seconds is the best option so you should keep it unchanged.