can i know how long a electric plane will stay up in the air???
That depends completely on how much fuel or what kind of a battery you have. Anything from two minutes to 30 minutes is normal.
I prefer the electric planes' to the Nitro one to get started off, and can you guys give me my best option, i want something, like a fighter plane, and something that can take off and land by it self,
You do not want a fighter plane as your first plane, unless you want to be sure you will crash immediately.
A GWS Slow Stick is a popular electric starter plane for those who cannot find any help. Even that should not be attempted before you have studied a lot (like here in the forums) and practiced on a simulator (a commercial one or a free one like FMS).