First ,,the word(yella) means come on ,do it, hurry up ,,and so on The 2nd word (besura) means quickly.readily, hurry up

same meaning , hurry up , but yalla it can be used only between close people and besuraa it can be used with strangers

even it's dialect , but Yallah is used in most all arabic coutries in standard arabic Fuus'ha , Ya Allah means : Oh ! God

Yalla is not standard language