Suggestions for 7 week Europe itinerary?

I'm planning to do 7 weeks in Europe later this year from December through to mid Feb! I would love people's thoughts on the time in each place, day trips, food recommendations, hostel recommendations or simply just advice for a first time solo traveller!

I'm doing Spain and Portugal with a friend who's living in Madrid and the Italy, Switzerland and Austria solo!

This is the timeline I was thinking:

Madrid (3 nights)

Lisbon (3 nights)

Porto (2 nights)

Madrid (4 nights)

Barcelona (2 nights)

Rome (5 nights)

- Day trip to Pompeii

Florence (4 nights)

- Day trip to Pisa

Bologna (2 nights)

Venice (3 nights)

Verona (2 nights)

Interlaken (3 nights)

- Day trip to Grindelwald/Launterbrunnen

Bern (2 nights )

Lucerne (3 nights)

Innsbruck (2 nights)

Salzburg (4 nights)

- Day trip to Hallstatt

Vienna (4 nights)

Author: Substantial_Can_6254