All sounds familiar Lenin.
To give the full tale for mine. I had same symptoms as you and had done all the other stuff - tensioners etc. Couldn't feel anything wrong with alternator when I spun it by hand, but I could just about make out that there were some minute metal filings around the pulley on the alternator, which confirmed that the pulley clutch was on its way.
So I was on the way to a garage to get this done when the noise got a lot worse (a lot, lot worse), i pulled over and opened the bonnet to see that the pulley was glowing red hot! Anyway garage fixed it (with a new alternator apparently) but 3 months later I had another noise - this time more of a whining that rose with engine revs, rather than the clack/screech/chirp of belt slippage. This time it was the alternator bearings themselves, so another garage and another alternator. My theory is that first time round the garage just changed the pulley and not the alternator, but the heat from the pulley running hot had damaged the alternator bearings which subsequently failed....but I'll never know!