Richtig: eine ganz neue Erfahrung Richtig: eine völlig neue Erfahrung It works exactly the same way as in English: "a really/totally new experience", i.e. "really/totally" is an adverb for "new". And since it's an adverb describing the adjective (and not an adjective describing the noun) it doesn't get conjugated in German.

As Susanne said, the "völlig" is an Adverb and does not relate to the noun, but to the adjective "neue". Only the adjectives in front of a noun have to be declined. so "eine völlig neue Erfahrung" is correct. eg. der große, starke Mann - der Mann ist groß und der Mann ist stark. Wie ist der Mann? groß und stark(the man is tall and strong - how is the man? tall and strong - both tall and strong relate to the man) but: der extrem starke Mann - der Mann ist nicht extrem und stark, aber der Mann ist stark. Wie ist der Mann? stark. Wie stark? extrem stark. (the man is not extreme and strong. How is the man? strong. How strong? extremely strong. - only strong relates to the man, extremely relates to strong) it is interesting, since völlig is a word, that intensifies other words, however it is not a particle, since you can decline it. e.g. das ist völliger Blödsinn (thats complete nonsense) you will often find "normal" adjectives as adverbs in front of other adjectives, when the adjective is a Partizip 1 or 2. eg. die schnell zufallende Tür (the fast closing door. what is the door doing? closing. how is it closing? fast) die weit geschnittene Hose (the widely cut pants. how are the pants? cut. how are they cut? wide) i admit, its not so clear, because you can always ask - what is the door doing? closing fast. - or - how are the pants? cut wide. - but i think you still get the idea. some more examples that are again not so obvious der stark aussehende Mann (no idea if he is really strong, but he looks strong, in this case you even need an adverb to make sense of the adjective - "der aussehende Mann" doesnt say anything) das neu gekaufte Auto (the newly bought car - you would not ask how is the car bought? new. although you could say recently i guess. anyways again it is just important, that the adverb refers to the adjective. maybe the car is old, but the action of buying it is new - or recent) again i think i made an easy thing more complicated than it really is.

Eine ganz neue Erfahrung ist richtig. "ganz" bedeutet "sehr", z.B: "Ich liebe dich ganz dolle" das bedeutet, dass ich dich sehr dolle liebe" Und "ganze" bedeutet "volume", z.B: "das ganze Haus / ein ganzes Haus" => Das ganze Haus verbrannt, das bedeutet, alles verbrannt. This one ist correct => Eine völlig neue Erfahrung