Hi, everybody!

It's my first time on a forum, and I'm very excited because it's about Switzerland!!!
I'm a brazilian doctor in love with Switzerland since childhood. In September I'm going to realize the dream of visit Switzerland (my first international trip)!
Then, I'd like to get any advices and suggestions to make this trip perfect!

IMPORTANT: I've decided to buy the SwissPass, and opted for hostels (because the prices!!!)
I love cooking, I love cheese, chocolate and fruits (berries).
I want to participate of an Alpabzüge during my trip!

The trip will be divided into 2 times: the first with a friend (3nd to 16th) and the second with another friend (16th to 28th).

I already planned the first part of the journey:
Day 1 - Arrive in Zurich airport in the afternoon. Stay in Zurich.
Day 2 - The whole day to explore Zurich. Leave Zurich to Schaffhausen and stay in Schaffhausen for 1 night.
Day 3 - Morning to explore Schaffhausen. Leave Schaffhausen to Saint Gallen (by boat). Noon to explore Saint Gallen and stay in Saint Gallen for 1 night.
Day 4 - Leave Saint Gallen to Vaduz. The whole day to explore Vaduz. Leave Vaduz to Davos in the afternoon and stay in Davos for 1 night.
Day 5 - Leave Davos to Saint Moritz and stay in Saint Moritz for 2 nights.
Day 6 - Saint Moritz
Day 7 - Leave Saint Moritz to Zermatt (Glacier Express), and stay in Zermatt for 2 nights.
Day 8 - Zermatt
Day 9 - Leave Zermatt to Bern (in the morning) and stay in Bern for 2 nights.
Day 10 - Bern
Day 11 - Leave Bern to Interlaken and stay in Interlaken for 1 night.
Day 12 - Leave Interlaken to Gimmewald and stay in Gimmewald for 1 night.
Day 13 - Leave Gimmewald to Grindelwald and stay in Grindelwald for 1 night.
Day 14 - Grindelwald and region. In the afternoon, my friend will leave to Zurich.

All suggestions and advices are very welcome!!!

I need to decide about the second part of the trip (Day 15 to day 27), and I want to include: the canton of Wallis (Rhone valley, maybe Brig), Montreux, Vevey (and the Lavaux vineyards), Genève, Lausanne (?), Gruyères, Lucerne and the canton of Ticino (Lugano, Locarno and Ascona).
My return date to Brazil is Setember 28th, from Zurich airport.

By now, thank you for your attention. I will be eagerly waiting for your answers!

Best Regards.

Days 11 till 14 are IMHO not very logical. Either you stay in Interlaken and take day trips to Gimmelwald and Grindelwald or you skip Interlaken and stay just in Gimmelwald and Grindelwald. Personally, I'd stay three nights in Interlaken and use it as a base to explore the Bernese Oberland.

take a lot of stuff to read for your boat trip from schaffi to st gallen. it takes long enough to get to stein am rhein. after 2 hours, i wanted to shoot the person who suggested it. after 3 hours i wanted to shoot myself!

Kudos to you for putting a significant amount of effort into planning your trip and then coming onto EF as an afterthought. Makes it much more enjoyable to help people who have first tried to help themselves. That being said, a bit more info on your interests would help us narrow the search - otherwise I'll assume you're looking for a little taste of everything.

Anyways, I can't help much for the first leg of your journey as it's a bit outside my stomping grounds. Although, while near Davos, I might recommend: Scuol for an amazing spa; the Swiss National Park if you enjoy hiking (stay overnight at Chamanna Cluozza); a cable car up to 3000m Diavolezza to see the glacier; or a taste of Romansch culture in Val Poschiavo.

For the second leg of your journey, I can also only really comment on Vaud/Geneva region. I personally would spend less time in Lausanne and Geneve as I don't think they have much to offer relative to surrounding areas/villages. Nonetheless, you'll find plenty on what to do by perusing EF. Off the top of my head: the walled town of Murten/Morat can be combined with the amphitheatre in Avenches (aka Aventicum) to visit one of the largest Roman settlements; Lavaux vineyards are a MUST in September and can be combined with Chateau Chillon on the lake (not to mention stunning views); try to get to the top of Dent de Vaulion or Rochers de Naye for some seriously gorgeous panoramas.

Lastly, spend some time looking into any festivals and events taking place around that time. There's sure to be something.