@juliohm1978 I guess you just don't have the codecs to play the videos. Check the topics below:

https://forums.opera.com/topic/37539/solving-the-problem-of-the-opera-browser-with-video-playback-in-ubuntu-and-similar-distributions-linux-mint-kde-neon/

https://forums.opera.com/topic/42185/the-videos-don-t-play-topic/