Big Thanks for Your answer.
It confirms what I deduced from lsp-server error I found in emacs day after I asked a question. I've changed the port as You suggested. (I have no idea how to change the port on the emacs-lsp-server).
Part of the problem was that, I supposed, there is no need to start up the engine to use the lsp-server. Im to nooby as a programmer to understand why is that. I suppose lsp-server is some kind of an object, not a library as I thougt, and must be somehow initialized to the memory.
However Godot must be started directly from emasc. If I start the engine from command prompt as usual, it shoots lots of errors, telling me the resource is not initilized and creates empty copy of edited script but with strange name: ".#NameOfTheSript.gd".
Anyway it started to work just fine for Me, even if Emacs with lsp-mode enabled seems to be a little bit slower. Now i think the meaning of "install lsp-mode on top of gdscript-mode" is: 1. Install gdscript-mode. 2. Install lsp-mode. 3. Open script You want to edit in Emacs. 4. Turn on gdscript-mode 5. Start Godot from Emacs. 6. Enable lsp-mode.
Thats it for now. I'm willing to dive the subject deeper beacuse Emacs and Lisp had thrown a charm on me.