Hi Sebastian,
You have a Fantastic trip ahead of you! Another member has just finished a lovely loop of the island and Tromsø. He sent me his Strava info.
Perhaps you want to get in touch with him?
https://ridewithgps.com/trips/126922804
Senja and Kvaløya are reasonably easy to wildcamp. The beaches are great to camp by. The most famous is Ersfjordstranda which has camping spots on the grass behind the beach. There is also a public toilet which you can’t miss! http://www.nasjonaleturistveger.no/en/routes/senja/ersfjordstranda/
Here is a bit of info about Senja (tunnel, food shops, places of interest, etc: http://www.ridewithgps.com/routes/41403964?privacy_code=WpZNLUWj42ZKc5Wq
Most Famous hikes with incredible views:
Segla: http://www.earthtrekkers.com/hike-segla-one-of-senjas-most-popular-hikes/
Husfjellet: http://www.ut.no/turforslag/1112313/husfjellet-632-moh
ps: Make sure you visit the islands of Sommerøya: /www.scanadventuretravel.com/tour/sommaroya/
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