As mentioned by @CopperKettle in a comment, "wild-goose chase" is the first idiomatic phrase that comes to mind. To send someone on a wild-goose chase is to recommend they pursue something unattainable. It can definitely be used in the context of getting rid of someone.
A "snipe hunt" is a similar idiomatic phrase, but it's specifically associated with sending a newcomer on an errand that anyone with experience would know is unachievable and nonsensical.
However, I'm not sure either of these is quite what you're looking for, as the element of disrespect with these phrases is pretty mild.
Another phrase you might consider, although I don't think it's a direct parallel to the Polish phrase, is "to blow someone off". "To blow something off" means to dismissively ignore something, and is a very generic phrase with a stronger air of disrespect. Furthermore, it can be used in the context of giving an empty, possibly evasive answer, with the specific intention of getting rid of someone. For example, if you were to ask someone out on a date, and they told you they're busy reorganizing their sock drawer that night, that would be a harsh blow-off. In the case of the senior developer telling a junior developer to "RTFM", the senior developer is blowing off the junior developer.
It sounds like you're looking for a combination of "to send someone on a wild-goose chase" and "to blow someone off", and such a phrase isn't coming to mind for me.