First, we simplify the subtraction of a negative number by adding the opposite:

(-5) + (-4) + 11 + 8.8

Now, we add the numbers:

(-9) + 11 + 8.8

Now, we add the positive numbers first:

11 + 8.8 = 19.8

Now, we add the negative number:

(-9) + 19.8 = 10.8

Therefore, the final answer is 10.8.