I am 18 and want to travel europe ALONE ?

as long as you are very wary and make sure you look after yourself and don't put yourself in stupid and dangerous positions you will be fine. It's good that you have contacts over there so you can touch base. I went travelling with a friend around australia, new zealand and fiji but we split up for some of the time to do our own thing and we were both fine. Other travellers are usually very friendly (although some are not so don't rely on it) and you will meet lots of people in backpacker hostels to hang around with. Have fun!