From where we change the distance between tracks and copper fill (requirement 0.25mm)?
Board setup -> Design Rules -> Net Classes: Clearance
Check also each zone’s own Properties, it has clearance etc.
The stable version of KiCad supports only one kind of clearance, namely minimum. Each gap between two items involve at least two clearance values, and logically the larger value is effective. In the Net Classes you define clearances for nets; in the zone properties you can define a larger value if needed for that specific zone.
In your case 0.25 seems to be a pretty generic value which for simple boards without high speed or high current should work in every place. It’s possible that only one netclass, Default, is enough, and the clearance is 0.25mm. The gap (clearance) can of course be larger. So, this is pretty simple for you.
thank you so much for response @eelik . This is what I looking for really helpful for me.
thank you so much for response @pedro.Its helpful for me.