Can't subdivide ??? Why ??

Please help.

like you see in the picture i want to make any ajustmants on the mash.
But in the left corner you see that I can subdivide, but on the left you see the selected box.I can’t subdivide this.

I think that it is a Ngon.
But what is the easy way to remove this whit out having to unwrap the texture again.

As you’ve said,it’s an Ngon.

That is one very messy model,i suggest you learn basic modeling before moving on to texturing.

It would be much easier to redo the model properly and then UV unwrap it.