Ok components I have are Shimano XT
bike is 2011 Rocky Mountain element

I just did a big race. And my gears are a bit messed up.

I can't get gears down to the smaller last 2 gears.
When I make adjustments in which chain gets in those gears. I lose in upper shifting and can't get to my lowest/easiest gear. I tried turning and fine turing all screws.

I even took off cable and put it back on, but still problems.
What is one way to start over? start fresh or like a way to reset the gear and adjustments so i can start over?
this is getting stupid
thanks all
last many times idid this, was able to get it done bang on
not this time
thanks