I can't subdivide

Support Modeling
1

I can’t seem to subdivide anymore, and it probably has to do with ngons, but I’m not sure what that is. I frequently started blender yesterday so i’m not really that educated with it yet.
Along trying to find a solution someone mentioned mark several points and press the J key, but it doesn’t seem to solve my issue still.
here’s a picture:

subdivition.png1171×768 29 KB

the marked ones are the ones that I want to subdivide.

2

Because they are ngons you are just subdiving the edges of the face

You could select the vertical edges and subdivide
You can connect two selected vertices with J
You can use the knife tool with K
You can add edge loops with Ctrl+R