First of all - in Polish "jak" serves to ask for an adverb, "jaki/jaka/jakie" - for an adjective, so I see no problem in the logic of the answer (with the use of an adverb). As mentioned by others, you can't literally translate most things (although it's done often for educational purposes), because if you intend to become fluent in a foreing language, you have to
1/ accept, then
2/ try to understand and finally
3/ to reproduce (imitate)
its logic (sounds almost like marriage plans).
Of course, when you're not serious about it, you can skip all of this and try to carbon copy as much from your native language(s) or from a foreign language you know relatively well, but such relationship won't be succesful.
"This car goes incredibly fast" should be "This car goes incredibly quickly". Fast is an adjective. You can't modify "to go" with it. :P
well, apparently you can :)
You can say "excellent" and be qualifying a noun ("I am excellent") or "excellently" and be qualifying the verb ("I am excellently"). The reason that the latter of these sounds stupid and wrong would, I believe,
OK, I may be completely out of my league (English has always been a hobby for me, never studied it seriously with all this grammar), but I'm with Mufasa (or her first intuitive response, because later she was lured by Sajmon to believe differently)
I think the root of the problem is that the English language is messed up a little (because of its evolution) in terms of grammar.
One word can be different parts of speech depending on it's position - the most common is a 2 nouns combination where the first noun becomes adjective without changing its grammatical form
1/ He threw a stone. (stone = a noun)
2/ He hit against a stone wall. (for me an adjective, but you may argue that it's still a noun, since the wall is made of stones, but then shouldn't it be "stones wall"?)
3/ The pavement has a stone look. (looks like stone, but can be made of plastic or other materials).
Why isn't a "real" adjective used in any of those sentences? Because the English grammar, thanks to its structure, doesn't have such need. You can have a similar construction in German, but you usually make one word of the two nouns (Stein = stone, Mauer = wall, so stone wall = Steinmauer).