I could not get the videos to work, and even if I could have they looked a bit shaky. There's no substitute for being there, especially with drivetrain problms. If by "I replaced the chain..." you mean that you personally did the work there are multiple errors that could lead to the problem you are having, and there could be other problems of which you are not aware. So there's no way to tell online how much of "an issue" it is. I would strongly suggest you have a shop correct whatever deficiencies there are - it's better than being broken down in Portugal.