Denied boarding

I have been denied boarding two times in a row from Copenhagen to Manchester, the first flight they didn’t let me on as it was overbooked.. they then put me on the next flight 8 hours later with an assigned seat and didn’t let me on again that one due to it overbooked. It was Ryanair, the woman shouted at me on the second flight gate and said I was being ridiculous and there is no seat for me even though it says it on my boarding pass and on her system it says standby so I am not sure what I’m expecting. I am in complete tears at how I’ve been treated and told I won’t get compensation for the second flight, what are my rights here?