Barcelona and Bayern Munich game is not in La Liga, and it will not affect them in La Liga. The only game that is capable of affecting Barcelona or increasing the chances of them maintain there position in La Liga is the game that they will play against Sevilla. The game willl be able to determine that, even though I know that Barcelona has the highest chance of winning the gam, but still that game will be able to get them more 6 points and with that they will be able to maintain there position even if they lost against Real Madrid. But that for mean they will get 6 points in Sevilla 
Yeah playing against sevilla is their main priority at the moment though Bayern game is also a top priority for them but that won't be in Laliga , if they win Sevilla in their next game then they will be maintaining their point towards realmadrid game . The elclassico match also matters but they only need draw to stay ahead of rsealmadrid and maintain their point as the first position on the table, I think after the Elclassico, Barcelona game will highly be more of winning if they don't relax in any game both in laliga and UCL unlike RM who's wil be facing Liverpool in UCL after facing Borussia Dortmund before the Elclassico... though laliga shouldn't be more of a problem for them too if they tend to improve their game.