Usually my ideas come very suddenly and I don't have paper or pencil by hand so I forget them; also, I do not know how to order these ideas in physics since they are for a novel in process, there are also many people who give me advice for this one, I do not know if I should add them to the same place. I would appreciate if you would give me advice for this situation.
If you are serious about your writing, you must make it a habit to carry some notetaking device with you. If you prefer to talk into your smartphone's dictaphone app, or jot down ideas in a notebook, or type into a tablet, is a question of personal preference, but notetaking is something that few writers can do without, so include it in your life. You don't forget the key to your home (I hope), so take care of your notebook/whatever in the same way.
As for how you keep your ideas in order, there are different options:
I use a notebook. Whenever I write something in it, I add a capital letter in a circle, which signifies the story (if any) the idea belongs to. So if I go through my notebook I can easily recognize the notes that are relevant. I strike out the notes I have used and that are not longer relevant, so I don't have to go through them again.
When I work on a story, I usually transfer all the relevant notes from my notebook to a file on my computer (and cross them out in the notebook). That way, all my notes for one story are in one place. In that file, I order by chapter number, if I know where they have to go in the story, so that when I write I look at all the notes under the relevant chapter numbers. Notes on plotting or characterization go into files named "plot" or "characters". Etc.
That's basically it. Just try what works for you. You must have some kind of order in your life (e.g. for school or your job), so use the methods you use there to keep your writing in order, too. I'm a list and file cabinet type of person, so I create lists and sort stuff into (virutal or real) files. Think about how you create order in your life.
It largely depends on the individual. Forgive me for lack of a better reference, but I think it will illustrate a point:
And yes, they use the old fashion pen and paper. You can see that they all have different styles of note taking.
In conclusion, it's probably a good idea to get in the habit of having a pocket book (at least) with you at all times. How you keep your ideas in order is largely up to you. Try different methods. But I would avoid using a mobile phone, because chances are you will forget you wrote it down in your phone anyway and it will get lost.
An additional comment to your question: author James Patterson says (and I'm paraphrasing here, I heard him say it in a video) if your idea is 'good enough' you won't even need to write it down, you'll remember it anyway.