Hi @Savva5C62
If you have made a selection with one of the selection tools and you can't move it with the Move tool ("V"), then the first thing to look at is to see if you are on the layer you expect to be on. One possibility is that you are on a layer that is transparent where you have your selection.
There are other reasons, so if this is not it, show a screen shot with your Layers and Tools panels as well as your options bar for the Move tool.
Jane