Led strip - keypad - control animations Problem

Hello.I have an arduino uno , a keypad 4x3 and a led strip that consists of 30 leds (5V).
I have done many animations with this led strip and now I'm using this keypad so that I control the colors , the animations & the brightness.
I will show you 2 animations
1st animation: Just colors.When I push number '1' on keypad,I turn on red (for instance) ,when I push again number '1' I change color and so on.When I push '*' ,I decrease the brightness of each color and with '#' I increase the brightness.No problem with 1st animation...

2nd animation: When I push number '2' , I turn on an animation that fade in and fade out all leds with green color (for instance). When I push again number '2', I change color directly and led strip continues with this rhythm with no problems.

Mix of 1st & 2nd animation: Let's say I push number '1' so I have RED color ,then I push number '2' led strip does it's job (fade in and fade out). But ,when I push again number '1' ,led strip continues fade in and fade out and after a lot of presses of number '1' (4-7 presses) , finally I go to 1st animation.

I told you a lot so that you can understand my problem and what I have done so far.

Code (a part of it):

#include <FastLED.h>
#include <Keypad.h>

#define LED_STRIP_PIN 13
#define NUM_OF_LEDS 30

CRGB leds[NUM_OF_LEDS];
int brightness = 255;
int pick_color_variable = 0;
int fade_variable = 0;

const byte ROWS = 4; 
const byte COLS = 3; 

char keys[ROWS][COLS] = { 
                          {'1','2','3'},
                          {'4','5','6'},
                          {'7','8','9'},
                          {'*','0','#'}
                        };

byte rowPins[ROWS] = {8, 7, 6, 5}; 
byte colPins[COLS] = {4, 3, 2}; 

Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );



// Number of colors: 18
CRGB array_colors[] = {CRGB::Red , CRGB::Green , CRGB::Blue , CRGB::Yellow , CRGB::GreenYellow , CRGB::DeepSkyBlue , CRGB::Olive , CRGB::Navy , CRGB::Magenta , CRGB::Orange , 
                       CRGB::DeepPink , CRGB::Chocolate , CRGB::Coral , CRGB::Indigo , CRGB::Cyan , CRGB::Purple , CRGB::White , CRGB::Black
                      };



void setup()
{
  FastLED.addLeds<WS2812B, LED_STRIP_PIN, GRB>(leds, NUM_OF_LEDS);
  FastLED.setBrightness(brightness);
  pick_color(array_colors[17] , 0);
  Serial.begin(9600);
}



void pick_color(CRGB color , int brightness)
{
  for(int i = 0; i < NUM_OF_LEDS; i++)
  {
    leds[i] = color;
    FastLED.setBrightness(brightness);
    FastLED.show();
  }
}


void fade_in_fade_out(CRGB color , char key , int b , bool UP , bool enable__ , bool keep)
{
  int var;
  bool _1 = false;

  while(keep)
  {
    if(UP)  // fade in
    {
      if(enable__)  // if true ,then (in case I have changed color) the brightness continues from the last value brightness
      {
        var = b;
      }
      else  // otherwise , brightness starts from the beginning
      {
        var = 0;
      }
      for(int k = var; k < 255; k += 3)
      {
        for(int i = 0; i < NUM_OF_LEDS; i++)
        {
          key = keypad.getKey();
          if(key == '1')
          {
            keep = false; // stop while loop
            _1 =  true;   // number '1' just pressed
            break;  // exit from inner for loop
          }
          else if(key == '2')
          {
            if(fade_variable < 16)
            {
              fade_variable++;
            }
            else
            {
              fade_variable = 0;
            }
            fade_in_fade_out(array_colors[ fade_variable ] , key , k , true , true , true);
          }
          
          else // if no key has pressed , continue your job
          {
            enable__ = false;
            UP = false; // This gets false , so that leds fade out
          }

          FastLED.setBrightness(k);
          leds[i] = color;
          FastLED.show();
        }
        if( _1 )  // if number '1' has pressed
        {
          break;  // exit from outer for loop
        }
      }
    }
    
    
    else
    {
      if(enable__)  // if true ,then (in case I have changed color) the brightness continues from the last value brightness
      {
        var = b;
      }
      else
      {
        var = 255;  // otherwise , brightness starts from the beginning (which is 255, cause we are in 'fade out')
      }
      for(int k = var; k >= 0; k -= 3)
      {
        for(int i = 0; i < NUM_OF_LEDS; i++)
        {
          key = keypad.getKey();
          if(key == '1')
          {
            keep = false; // stop while loop
            _1 =  true; // number '1' just pressed
            break;  // exit from 2nd for loop
          }
          else if(key == '2')
          {
            if(fade_variable < 16)
            {
              fade_variable++;
            }
            else
            {
              fade_variable = 0;
            }
            fade_in_fade_out(array_colors[ fade_variable ] , key , k , false , true , true);
          }
          
          else  // if no key has pressed , continue your job
          {    
            enable__ = false;
            UP = true;  // This gets false , so that leds fade in
          }

          FastLED.setBrightness(k);
          leds[i] = color;
          FastLED.show();
        }
        if( _1 )  // if number '1' has pressed
        {
          break;  // exit from 1st for loop
        }
      }
    }
  }
  if( _1 )  // if number '1' has pressed
  {
    pick_color(array_colors[pick_color_variable - 1] , brightness);
  }
}


void control_brightness(char key)
{
  //char key = keypad.getKey();
  if(key == '*' && brightness > 0)
  {
    brightness -= 15;
    FastLED.setBrightness(brightness);
    FastLED.show();
  }
      
  if(key == '#' && brightness < 255)
  {
    brightness += 15;
    FastLED.setBrightness(brightness);
    FastLED.show();
  }
}




void loop()
{
  char key = keypad.getKey();
  
  if(key == '1')
  {
    if(pick_color_variable < 18)
    {
      pick_color_variable++;
    }
    else
    {
      pick_color_variable = 1;
    }
    pick_color( array_colors[ pick_color_variable - 1 ] , brightness);
  }
  else if(key == '2')
  {
    fade_in_fade_out( array_colors[ fade_variable - 1 ] , key , 0 , true , false , true);
  }
  
  control_brightness(key); 
}

I think it's a problem of breaking 'for loops' or 'while loop'. I 'm testing it for about 3 hours now and I can't figure it out.

Your help is appreciated a lot.

Thank you.

Answer (a part of it): Get rid of the for and while loops.

So, what loop should I use?

The one called loop().

That's not help me ,because I want to change color or animation any time I want inside fade_in_fade_out() function and this can't be done inside void loop() I guess.
Otherwise,I had to wait for a function to terminate and then start a new animation or change a color.

Ok,problem solved,I had to create some new boolen variables,delete others and change some parts of code and now it works as I expected.