How I manually fix my grass mesh normals so all textures are visible?

have been exporting models from blender to the hammer editor recently and have come across a problem with this particular grass model:

Some of the grass wasn’t visible in the editor I was exporting it to and I looked in the face orientation view to find that most of the inside of the model was red, meaning it wouldn’t be visible once exported.

I then tried to recalculate my normals outside in edit mode. This was the fix I did before when I had texturing problems, but with this mesh, little to no change is seen when I do it.

Before:

After:

I also tried recalculating inside but it gave me the same problem with the texture but now on the inside instead:

I asked in a chat about this and people said I need manually change my normals. How would I do this so both sides are visible? When I select a face, it selects both sides i.e the red and blue side. Will this be a problem when I’m changing them?