i am editing a tab and i am trying to add more notes to a bar but what happens is the bar either turn red or the notes i add wont play. i am kind of a noob at tabbing on guitar pro.
The 'math' of your notes has to be consistent with your time signature and the bars turn red if they are incomplete or otherwise mathematically inaccurate. If you haven't ever studied music, it can be incredibly daunting to use this software to it's maximum potential.

Good luck
Red bars mean that the notes don't add up to fit the bar. It means your durations are off rhythm/time or you didn't put in rests where needed. You should either read about note durations and time signatures or do trial and error until they are (and sound) correct. If you're adding a note to a correct full bar, you must change another note's duration.