Is it possible to change the taskbar

I don't have a problem but i would like to know if its possible to stop the taskbar from hiding when in fullscreen in things like firefox?

fullscreen hides always every taskbar, even a taskbar that is fixed, and does not automatically hide. Maximized windows are not to be confused with full screen.
You can right-click the taskbar and go edit mode to choose its behavior, and also welcome here : - )