Note that it is spelled Kiso.Where is the station I should leave my luggage and turn round to pick up?
Are you referring to the luggage forwarding service? Drop-off and pick-up locations are the tourist information centers in each town. Note that the forwarding service is not offered every day of the year.
How long time to spend in Narai, Tsumago and Magome?
Depends on personal preferred pace of travel! People who like a fast pace can visit all three towns in a single day. Others who prefer a slower pace, take two days.
Can I get the timetable of direct buses from Tsumago to Magome?
Here you go:
http://www.japan-guide.com/bus/kiso.html
One choice, I could send my luggage to nagoya but I don't know how many day I'll receive my luggage.
Takuhaibin deliveries generally are made on the following day:
http://www.japan-guide.com/e/e2278.html