Thanks for your answers.

I created a "init.el" file in ~/.config/emacs

and a "custom.el" file in the same directory.

I moved my .emacs.d to ~/.config/emacs and deleted later the empty 
~/.emacs.d directory and the ~/.emacs file.
-------------------------------------------------------------
So, I have now everything in the ~/.config/emacs directory

directories:

auto-save-list
eln-cache
elpa
tutorial
url

and the files:

custom.el
init.el
misterioso-theme.el
-------------------------------------------------------------
custom.el:
(setq custom-file (expand-file-name "custom.el" user-emacs-directory))
   (load-file custom-file)

(custom-set-variables
  ;; custom-set-variables was added by Custom.
  ;; If you edit it by hand, you could mess it up, so be careful.
  ;; Your init file should contain only one such instance.
  ;; If there is more than one, they won't work right.
  '(ansi-color-faces-vector
    [default default default italic underline success warning error])
  '(ansi-color-names-vector
    ["#2e3436" "#a40000" "#4e9a06" "#c4a000" "#204a87" "#5c3566" 
"#729fcf" "#eeeeec"])
  '(custom-enabled-themes '(tsdh-dark whiteboard))
  '(font-use-system-font t))
(custom-set-faces
  ;; custom-set-faces was added by Custom.
  ;; If you edit it by hand, you could mess it up, so be careful.
  ;; Your init file should contain only one such instance.
  ;; If there is more than one, they won't work right.
  '(default ((t (:family "DejaVu Sans Mono" :foundry "PfEd" :slant 
normal :weight normal :height 120 :width normal)))))

-------------------------------------------------------
init.el:
;; Display line numbers in every buffer
(global-display-line-numbers-mode 1)
--------------------------------------------------------
1. question

So, as far as I understood you, I should do all my customisation in my 
custom.el file and not in the init.el file.
What goes than in my init.el file?

2. question

I have got a "misterioso-theme.el" file in my ~/.config/emacs directory
but it doesn't work now.

Should I simply delete this file, and create this theme new?
If so, what is the best way to create this theme or an other?


Kind regards

Gottfried