Does Google Disavow really work and how much time doest it takes to Disavow bad backlinks?

1) Do google disavow tool really work?

yes, google disavow tools really work like a charm but before that I would recommend you to request all the people of the website from where you have got the backlinks, to remove it from their website because it used to not look good to see the spammy backlinks link to your website.

2) How much time will it take to disavow bad backlinks.

So, it depends upon the number of backlinks to your website if is less than it will be done within few hours or days but if it is more than sometimes it used to take month also because it takes time for Google to get around to reading your list, analyzing it, and applying it.

and one more thing when you upload a list of links before that you have to remove the links which you have uploaded earlier.

In my experience, I have Seen one of my clients was having approximately 1 thousand spammy backlinks and it took about a month to disavow the backlinks.

Now, I will be taking your 3rd question, after what time will google search console stop showing disavowed links.

I will say it again it depends upon the number of backlinks you have connected to your website.

Hope this helps.