Implementation of Big numbers division

Question

I develop own big_int class. It is a study task. I implemented +, -, and * ops. It works well and fast. But I have some troubles with implementation of big numbers division.

I implemented division, as the difference between the numbers (pseudocode):

big_int division (big_int first_number, big_int second_number) {
    big_int counter = 0
    while (second_number <= first_number) {
        first_number -= second_number;
        counter++;
    }
    return counter;
}

It works only for small numbers. But my test numbers have length not greater than 100.

I present my number as array with base = 10. For example, 113 equal to number[3] = {1, 1, 3};