The Nick Risuena is not registered so if you are using it and anouther user comes in and tries to use it they will be renamed Risuenaxxxx random numbers represented by x.
This will also happen if you get briefly disconnected and reconnected ... and I suspect may be what happened to you.
I do suggest you use /join #support who will help you register your name, once you have logged in ... just make sure you change to the nick you want to register before you try to register (I've seen that mistake made many times
At times you will find you can not connect. It may be worth checking what name you have in tools > options > community chat .... if you change it there you need to restart FrostWire before it takes effect.
I hope that helps for now. I'm not saying too much as I fear I might get you a bit more confused