Having a problem with rand function and pointers in functions

#include<stdio.h>
#include<time.h>
#include<stdlib.h>
float polje(float a[]);
int main()
{
    int n;
    float a[n];
    printf("%d",polje(a));
    return 0;
    
}
float polje(float a[])
{
    int n,i;
    scanf("%d",&n);
    srand(time(NULL));
    for(i=0;i<n;i++)
    {
        a[i]=(2*(-n))+rand()%((2*n)-(-2*n)+1);
        if(a[i]>=n && a[i]<=0) i--;
    }
    return *a;
    
}

I need to make a programme with a function that will give me random numbers from -2n to 2n excluding numbers from n to 0. I need to allocate the memory for 800 float characters but I dont know how to do it. The compiler only warns about one mistake but im aware that the whole code is a mess.

9 5 C:\Users\x\Documents\saff.cpp [Error] cannot convert 'float' to 'float' in assignment