The step from B2 to C1 is the one you cannot take by studying more grammar. At B2 you already know nearly all of it. What is missing is something else, and that is why so many people sit at B2 for years.
What actually changes
Precision instead of working around it. At B2 you always have a way of saying what you mean. At C1 you have the way: the right word instead of the detour. The difference between «the thing you use to open wine» and «a corkscrew», scaled up to a whole conversation.
The unsaid. At C1 you catch what was not stated: the irony, the allusion, the weight inside a flat «certo, come no». This is the part grammar does not teach and textbooks do not explain, because it lives in context.
Register. Knowing that siccome and poiché do not belong in the same sentence, that an email to a public office should not read like a message to a friend, and that formal written Italian has a rhythm of its own.
Length. At B2 you can hold a paragraph. At C1 you hold a stretch of discourse: three minutes of argument with a shape, not three good sentences in a row.
The test that exposes B2: retell a film you have seen, out loud, without stopping, for two minutes. At B2 the retelling works but flattens into the present tense and a chain of «then». At C1 there are time layers, things flagged in advance, asides.
Why B2 is a comfortable trap
Because it works. At B2 you live, work and argue in Italian with no serious trouble, and outside feedback disappears: nobody corrects you any more, because correcting you would be pedantic. From there improvement stops arriving on its own. You have to go and find it.
It is also the point where the tools that got you here stop being enough. Apps, general courses and multiple-choice exercises are built to take you to B2. Beyond it you need harder input and someone who will tell you where you still sound foreign.
What actually works
Reading things that are badly written on purpose. Not only literature: minutes of meetings, contracts, local news, comments under posts. Real language has registers that textbooks avoid, and C1 lives inside them.
Writing, and getting corrected. Not speaking: writing. Writing is the only place where your mistakes hold still long enough for someone to show them to you. Half a page a week, properly corrected, is worth more than ten hours of free conversation.
Collocations. At C1 you do not get words wrong, you get pairings wrong: you prendere a decision and never fare one, you nutrire a suspicion, you correre a risk. They are the hardest thing to pick up alone and the fastest to fix once somebody points them out.
How long it takes
Longer than any other step: eighteen months to three years, and the main variable is not how much you study but how much difficult input you take in. People who read widely and get corrected arrive. People who keep doing exercises stay at B2 with harder exercises.
Before aiming at C1, though, it is worth checking that you are genuinely B2 across all four skills and not just two of them.
