'Yeah, at least I want them to put more in on the second floor... wait, why are you here?!' 'Why? Isn't it obvious? So we can go to the bathroom together.'
Literal
''Yes-yes. At-least 2nd-floor [locative-にも] increase want-[quotative-って] why you [subject-が] here [locative-に] exist!?'' ''Why [quotative-って], such-thing [topic-は] decided is-[Kansai-やんか]. Together take-pee-go [for-ため] is [Kansai-や].''
Kansai dialect heavy. やんか is the Kansai equivalent of じゃない ('right?', 'isn't it?'). や at the end is the Kansai copula (standard だ). そんなん is the Kansai contraction of そんなこと/そんなの. 連れション is slang for 'going to the bathroom together in a group' — literally 'accompanied peeing', a well-known social pattern (especially among women). The stage shift from calm conversation to 'wait, why are you here?!' is a common comedic beat.