This is actually a structural inversion sentence. I'll translate this sentence into a normal sentence for you. You should be able to understand attributive clauses, right US President Barack Obama and Barcelona's football team are both non-restrictive attributive clauses, so let's put them aside.

In fact, US President Barack Obama and Barcelona football team have been there. Pay attention to have in the original text, because the subject is tied for two, so the plural predicate is used. Do you understand the sentence structure?

Those changed travel plans include that the President of the United States arrived in London one day earlier than scheduled, and Barcelona arrived in the British capital (London) ahead of schedule to play in the Champions League final against Manchester Company on Saturday.

Early doesn't have to be translated, because it means earlier than the scheduled date with ahead. Translate only one word, and the translation will be very early. Clash means conflict, conflict means confrontation, then the conflict and confrontation between football teams is a game, so the final conflict means the end, and confrontation means someone. Generally used in wars, battles, competitions, challenges, etc. ~

So, have you solved your doubts? If there is anything unclear, please leave me a message.