Beginner Gardening: Beginning steps for slope landscaping needed - Preparation, 0 by Clementine

Clementine wrote:
Hello, me again:
I have started working behind the wall. I am putting 3' landscape fabric down along it (difficult in the corner where the steps come down), and my question is this: how high should the fabric come up behind the wall? I am enclosing pictures to describe what I mean.

Now I am putting in soil, then I will cover it with mulch. I don't think I can put anything into this "ditch" behind the wall, it is not going to be deep enough, but I will ask you about that later, if I may.

The picture attached here shows what I have done. Right under the cardboard (protection) is the capstone (about 3" high). Under it, there are holes between the building bricks which on this picture I have tried to block with a piece of bigger stone, because I thought the soil I am putting in would push the fabric down into the hole.

Am I making a mountain out of a mole hill?