So Im now a 6 Digit Player Rank (350.000) and i can't double tap so this means I can't get better so how can i learn double tapping the easyiest way or is there even a way ?
if you mean alternating between your fingers every note then focus on alternating your tapping and play easier maps.
if you mean not being able to play burst or streams (patterns that require you to use 2 fingers) then I have no tip for you as you just need to keep playing them until you get used to it (muscle memory)