Well, what do you like?
Architecture, scenery, food, cafes, bars, museums?
I suggest you do a Search of these countries and see what comes up that interests you.
Generally, many travelers try to spend close to a week in each country, but I’ve broken that rule before and probably will again.

Thanks for the advice .Um i’d love to see the scenery and also get a sense of the history and culture of each place. So you find that spending less than a week in each place is do-able ?

I would not do Italy for less than a week. I spent 16 days traveling by train and still left with places I wanted to see. For Italy must sees: Amalfi coast, Rome, Venice (depends what you like. I loved Venice but know people who loathed it).

Greece: Islands. Santorini and Paros are nice.

Germany: Munich is beautiful and very fun. I’d spend about a week in the Bavaria region

Where are you from? You may need a visa to visit Russia. That involves some time, expense and planning. You may need a letter of invitation which means you’ll have to have reservations for your lodging well in advance. Also, while the situation is better now than it was last summer, Russia is incredibly expensive. Moscow is one of the most expensive cities in the world.

Are you traveling alone? I don’t recommend driving for solo travelers as it will be significantly more expensive than taking the train. Driving “in a foreign language” is a full time job for 1 person. “Spotting” (looking for signs, road markers, parking places, etc.) and navigating/map reading is a full-time job for another person. A car is great for exploring the countryside or getting to know a non-urban area, but the train is faster and usually cheaper and more convenient for getting from city to city — plus having a car is a nightmare in most big cities.

In Greece, Santorini, the best island in the world!

I would spend at least a week in each country on average, otherwise you’re going to end up not even remembering what country you’re in.

The visa to Russia is such a hassle that it really isn’t worth it unless you go for a couple of weeks (it’s a big country anyway, I went for 2 months and still saw very little).

In Serbia, at least go to Novi Sad and Belgrade. If you want scenery, the Djerdap national park is good. Lepenski Vir in the national park is one of the oldest archeological sites in Europe, very interesting. Nis is worth a visit too, if only for the skull tower.

Germany’s big, so if you only want to spend a week, pick one area. Berlin alone is worth a week.

In Greece, I’ve only been to Crete, which is very touristy but nice scenery and archeological sites. But on a whirlwind trip like this, it’s probably better to stay on the mainland, less time needed for transport.

I really don’t think you can see all of these countries in 4-6 weeks.

All European countries are worth visiting! I recommend to add Czech republic – Prague and Cesky Krumlov – big history, nightlife and cheap. Also Spain – Barcelona!

I agree with Marekk, absolutelly dont forget to add Czech Republic..amazing country with pretty cheap beer ..