My iphone 11 promax i bought 25 days ago and now maximum capacity shows %99 percentage please help me!

Nothing to worry about.

See this similar answer provided by our colleague Alancito:--> "Maximum battery capacity measures the device battery capacity relative to when it was new." ...So not relative to when you bought it. Also, in measuring a chemically dynamic process such as in a battery, it's unlikely that the estimate can be accurate to within 3%. Read more in this Apple Support Article:--> iPhone Battery and Performance

Regards

Giulio