i just replaced everything on my firebird phantom by hobbyzone and i need some tips on flying it

Level flight will happen at a speed determined by what speed or throttle setting you trim for level flight usually around one third to one half throttle. make SURE it balances correctly front to back AND wing tip to wing tip. launch it straight out with wings level at half or just a little better than half throttle into the wind (this is not a good windy day airplane). don't turn until you are up a ways then turn with SMALL stick inputs. GOOD LUCK try trimming for level with a few level glide tosses power off to get a nice straight glide this may help get you close to power on trim positions.

thanks alot

If you trim it too high it will scallop the flight. The plane is not very controllable at the apex of the scallop where it has momentarily stalled.

Keep your control throws LOW. That thing is very fast and very sensitive