Thank you all for your kind responds and informations.

It's a shame I can't understand bulgarian and I'm happy you gave me all these informations in english.

1. As for the propositions of walking together: I would be delighted and it really would be more interesting for me. But there are some obstacles, I suppose. I will try to explain. I'm not that young anymore, so I know that there's not enough time left to me to see so much as I would like. That's why I try to spend the most time walking. It means sometimes even 15 hours a day. I can't tell the exact day, hour or place, where I will be able to come with my car and then start walking. It would be then difficult to fix an appointment.
I will be in Bulgaria two weeks in the second half of June (I hope, the weather will be good ;) ). I know it's rather small amount of time to see that much. But still, I hope I can have a glimpse at all the mentioned mountains and I'm even thinking of one day for the Slavianka in Rodopi (I've seen photos but don't know yet, how far it would be from Pirin).

2. Pirin: if it's possible to come to Sandanski hut with the car - it's wonderful! It is really a good starting point for the ridge from Kamenica to Wihren.
I would like to visit also the northern part up to Suhodolski Preval and don't know if it's better to make the ridge from Wihren hut to Suhodolski Preval rather starting from Bansko than from the west-south.

3. Rila: For Musala the best starting point is Borovec, I believe. For the western part it seems that the Rilski Monastir is the best.

4. Stara Planina - Kaloferska: I'm thinking of a veeery long trip: Karlowo - Ravnec - Rajsko Praskalo - Botev - Goljam Kupen - Karlovo. How long would that trip be? 16 hours or more? I've heard about beauty of the Dzendem. Can it be seen from such a trip?
Stara Planina - Tetevenska: Are there any bus connections between Srednogorie - Anton - Klisura? Or only the train?
Where could I cross with the car the ridge from north to south near Tetevenska and Kaloferska Planina?
Where can I buy the maps of Stara Planina? Only in bigger towns or also in smaller ones?

Wojtek