Hi Dieterkyra!  What kind of help are you looking for?

Subtracting negative numbers is equivalent adding the positive forms of the number you're subtracting.  For example, 5 + 6 = 11, and 5 - -6 also equals 11.  

Yes, it's still subtraction, but it's kind of like a double negative: you're taking away negativity, which means there is more "positiveness", resulting in a higher number.  

There are different ways to visualize this, so if you're still confused, I can show you another way to view the idea of subtracting negatives.  

Khan Academy also has some useful videos on the topic.  

When dealing with subtraction of negative numbers it is helpful to expand the meaning of subtraction from simply "taking away" to "what must I add to".   As follows:

Given. 9 - 4 your currently think "9 take away 4 = 5", but to accommodate the subtraction of negative numbers it is more helpful to think "what must I add to 4 to equal 9?"  Again the answer is 5.

Now let's apply that broader meaning of subtraction to:

9 - -4 =  ?   "What must I add to -4 to equal 9?"  If you view the number line with the points for -4, 0, and 9 depicted, it's clear to see in moving from -4 to 9, you can move 4 units to get to 0, and 9 units to reach 9. So you've had to add 13 to -4 to reach 9.   9 - -4 = 9 + 4 = 13.