It’s probably impossible to say with any certitude. I think your age matters, so that the younger you are the better and easier it is. The Defense Language Institute in Monterey, California, says that to go from 0-fluency (however they define that) in one of the Romance languages or one closely related to English (they’ve got Dutch and Afikaans on the list, for example), you need 600 hours of study. They refer to those as a category 1 languages, which are, they say, the easiest for a native English speaker to learn (they don’t use the „A-C”ranking system used here, and I suppose internationally, to my knowledge. I’m not a fan of the “A-C” rating system myself only because I find the definitions of each level as vague and ambiguous. Hours of actual study or years of use of a language tell me much more). But, I can’t see any reason why the 600-hour rule couldn’t apply in your case. So, if you took courses totally 25 hours per week over a 6 month period I would imagine you’d be at a reasonable level of fluency in 6 months.
As someone who is trying now to learn a new language and is currently getting frustrated by what I perceive as not good progress, I can tell you that learning a new language will take time. Of course we'd like to make progress faster, but the point is not to get frustrated, and to learn go appreciate little victories and signs of progress that we see along the way.
As some guidance, I can speak with some degree of fluency 6 languages, and only in three of those do I feel like I'm "good enough". The first one in my native language of course, then English, which I learned as a kid, and then Portuguese. Even when Portuguese is a language that's quite close to my native Spanish, it took me around a year to get to the point where I felt I was speaking pretty well.
So, my point is: is it possible to be fluent in 6 months or less? Probably, but if you don't get there, just keep learning and practicing and you'll get there for sure :)
Here is an video, i should watch it, i think this will help for you :)