Hi and welcome to TT.
If you're looking for travel companions, you may want to post as well in the Travel Companions branch. I also recommend that you join Couchsurfing and Hospitality Club. They've always been great resources for me when I have travelled solo. Just be sure to use them for cultural exchange, and not just to get a free bed.
Since you mention trains, Man in Seat 61 is the first website you need to visit. Click here.
If you're looking for more advice, you may want to give us more information. As a new TTer you'll find that the more specific you are, the greatest and most useful advice you'll get. Would you like to tell us, where exactly in Europe are you thinking of going, how long are you planning to travel, your interests and your budget (in euros)? That way, you'll help us to help you.
If you don't have any specific questions, I recommend that you browse past threads started by other people asking for general information on do's and dont's, how to plan their first trip to Europe and the like.
Looking forward to hearing more about your travel plans.