Arduino leonardo

Hello,

I'm using a Arduino Leonardo, but when i try to program it, it lose connection. Somethimes it works then it doesn't.
also when i use the serial monitor, it won't work al the time.
Desktop can't find COM port.

When i use my Arduino Uno everythings works fine.

Is this Leonardo just a bad arduino? or what can be the reason for my problem.

Is this Leonardo just a bad arduino? or what can be the reason for my problem.

I don't think so.
Much probability the problem is in your computer(windows, drivers....)
Did you already try in another computer just to see what is the behaviour there?