Law / Need help with Allegro in Poland, I'd like to sell a few things. [5]

Hello,
I am form Lithuania, I speak Russian and English. My Polish is pretty bad.
I would like to sell few things on Allegro.

Could anyone answer few questions?
1. What are costs selling on Allegro? link would be useful
2. If I have bank account in Lithuania, can I use it, or it is better to go to Poland and open Polish bank account?
3. I read that there is Allegro payment system. Do I need it? or maybe it is easier just to have Polish bank account and that's it?

4. If I will have Polish bank account will buyers trust me?
5. Maybe there is something specific wich I need to know for selling on Allegro?

Thank you for answers.