But can I add this information just because I think that this is the question? I mean, this example is obvious, but there could be questions where I add false informations I think are correct.
Well, instead of editing the question to add missing information, you rather should leave a comment for the OP to clarify and improve their question (as you did already).
I could add "I use Discord.js for a Discordbot I create, but he refuses to play music in a voicechannel". But this information could also be wrong. Maybe the bot doesn't refuse, it just won't activate in a specific channel. How far should the improvement go?
As you mentioned such edits may quickly become speculative and obfuscate the real problem stated in the question.
The purpose of question edits is more to improve grammar, clumsy wording and style (e.g. correct formatting), not to add missing information.