Florence,Venice,Paris,German Alps

Italy to France then back to Italy ???

Go Florence to Venice ( train ). Venice to Munch ( train ). Fly Munich to Paris

I agree about Florence to Venice by train.

Then take a train from Venice to Innsbruck where you'll be in The Alps--a few miles south of Bavaria. The mountain scenery is even better there. Most people would take a train Innsbruck-Munich and then fly to Paris on AIr France or Lufthansa.

Or, you could fly Innsbruck-Paris on Air France.

You've asked about things to see in Paris in a separate post so it's probably best to limit the 'main sites' stuff to that thread.

I'll absolutely agree with a Florence> Venice> Germany> Paris route. Venice is only 2 hours, 15 minutes from Florence by fast train. You'd kill FAR more time dealing with airports, both TO Paris and then BACK again to Venice. The train will also drop you off right IN Venice (S. Lucia station) versus out by the airport.

If Florence is your first stop, I'd give it at least 3 nights, especially if coming from the U.S,, Canada or other overnight flight. Your arrival day - which would only be a partial - could be a jet-lagged fog so best to have at least 2 FULL days to work with. I'd even give it more if interested in taking a day trip to Lucca or Siena or a number of other reasonably nearby destinations.

Train to a Bavarian base, and then fly to Paris. As suggested, Innsbruck (under 5 hours by rail from Venice, I believe) would provide some impressive alpine scenery. I was there many years ago and remember it being very pretty!

Have you bought your airfare?

Why not go to the Italian Dolomites instead of the German Alps? That way, you could minimize travel time again. I'd go F->V->Dolomites->Milan Airport->Paris

Thanks for the advice! I'm flying into Florence and out of Munich. We're going to the Bavarian Alps to see our dear friend who was our host for a year in the US as our au pair/family member 12 years ago. We've been meeting her on different adventures and this will be our first time in her hometown. Paris was an afterthought and we will burn some time traveling. I'm traveling with my 17 and 20-year-old sons and we thought of staying in Italy and then going to Bavaria. Paris sounds too wonderful to pass up. I haven't made definitive plans to go there and if anyone has other ideas that would be wonderful to stay along the same route, I'd think about other suggestions. The back story is that my husband is a Boy Scout leader and is going to Italy for an awesome adventure with the Scouts and my boys and I wanted our own adventure and we're meeting up in Germany. Thank you so much for the advice

If the flights are all set and cannot be changed, then I would do Florence - Venice (by train) - Paris (by plane) - Munich (by either train or plane).
It seems like the most efficient sequence to me.

Thank you so much for the responses. I booked all hotels and will wait on train tix and start looking for flights to and from Paris.

I booked all hotels and will wait on train tix and start looking for flights to and from Paris.

If you’re going to the Bavarian Alps, Venice, Florence and Paris fly into or out of Munich and Paris. This is known as an open jaw (multi-city when booking airfare). Furthermore, your plane tickets should have been purchased before hotel bookings were made.
Since you’re visiting friends in Germany, will your friends drive you to the top sights in the Bavarian Alps? If not, you’ll need to rent a car to appreciate it.
You can take a direct overnight train from Munich’s Hbf to Venice’s Santa Lucia station (end of line) and rent a sleeper car. This way you kill two birds with one stone. You may be able to buy train tickets six months out and the further out you buy the cheaper it is.
From Venice’s Santa Lucia station there’s a direct train to Florence’s SM Novella station (2h 15) and then fly nonstop from Florence to Paris ORY that’s closer to the city than CDG.
Ask your friends how long you need to stay in the Alps. In Venice you want three nights, Florence four nights and includes a day trip to Siena by direct bus (1h 15m) and Paris five nights.

I'm confused.

You ask how many days in places yet apparently that's irrelevant since the flights and hotels are all bought and paid for. What's left to decide.

I have all sorts of ideas for rearranging but if its all set in concrete there's no need.

booked all hotels and will wait on train tix and start looking for flights to and from Paris.

hotels are all bought and paid for.

Where does it say hotels were paid for? How do you know the reservations cannot be changed?

Good that you are departing from Munich. I would fly out from Munich too.

Munich (MUC) is highly regarded as an airport, which I had read about prior to being there. When I had to fly back to SFO in 2014, there was a direct flight from MUC. Seeing that airport I could see why MUC is rated so highly.

Fred, OP said:

start looking for flights to and from Paris

Logistically this takes longer.