Bring a Berner puppy home and the first thing you notice is how much they sleep. Sixteen to eighteen hours a day is normal, and interrupting it causes more problems than any training mistake. Build the day around rest and everything else becomes easier.
Weeks one and two are about safety and routine: the same feeding times, the same toilet spot, the same quiet place to sleep. Expect a broken night or two, and expect your puppy to want to be near you constantly. That devotion is the breed, not a phase to train out.
By weeks three to six you can start short, positive introductions: the car, a visitor, a soft brush, a lead on the floor. Keep each one brief and end while it is still going well. Growth is rapid now, so weigh weekly and adjust food to keep your puppy lean rather than heavy.
Around three months the confident phase arrives. Manners matter more than tricks: no jumping, four feet on the floor for greetings, and calm as the household default. A Bernese Mountain Dog who learns those things at fifteen kilos will still remember them at fifty.