Co jest nie tak z tym "else"?

You mean something like this:

package pl.codegym.task.task02.task0214;

/*
Mniejsza z dwóch liczb
*/
public class Solution {
    public static int min(int a, int b) {
        int m = 0;

        if (m<a,b);
            {
            return m;
            }
        else (m>a,b);
            {
            return m;
            }

        //tutaj wpisz swój kod
    }

    public static void main(String[] args) throws Exception {
        System.out.println(min(12, 33));
        System.out.println(min(-20, 0));
        System.out.println(min(-10, -20));
    }
}

Wyrzuca błąd.

not a statement.
file pl/codegym/task/task02/task0214/Solution.java, line 14, position 248

That's how I just thought if it wasn't supposed to be ";" with else if I would delete ";" on line 8. In the examples in the network there was finally no semicolon ";" in the examples, and I initially suggested hints in the previous help topic for this task. So I removed ";" in my original solution in line 8. And it worked. One unnecessary character. If they also removed in your second way would it work? (only in the task I have to compare the values of a and b, if I add the variable "int c" with the value e.g. 0. I may not meet the conditions of the task.)

Do something like that: if (a<b) m=a; if (a>b) m=b; return m

Thanks.