Tickets to Sevilla v Barca last game in May

Hello and thank you in advance for the assistance. Hablo español si es más conveniente. I will be traveling with my family (wife + 3 teenagers) to live in Spain for 6 weeks in late May. I would like to see the last Barca game of season, which looks like in Sevilla. What is the best site to buy tickets (I’d like good seats… probably will be the only time I see a la liga game). When will the Sevilla game date be confirmed and when will tickets go on sale? Do you have any recommendations on website to purchase them? Thank you again.

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