"어떻게든": "Anyhow", "Somehow", "By any means". "-거든": "If", "When". ~It is not really used that often. It's kind of a literary style ending. e.g.) If you meet him, tell him to call me. : 그를 만나거든 나한테 전화 하라고 해. You may leave when you have done with cleaning. : 청소를 다 하거든 가라. ~It's also used when you want to tell someone something. So, it's just another way of describing and explaining. I think it's more commonly used than the first case. e.g.) We can't give you a discount. Our prices are fixed. : 할인을 해드릴 수 없습니다. 정찰제거든요(정찰제입니다). It might be hard to cook for me. I'm a vegetarian. : 나한테 요리해 주기가 까다로울 지도 몰라. 나는 채식주의자거든(채식주의자야). I couldn't participate because I didn't get the notice either. : 나도 그 공지를 못 받아서 참가 못했거든(못했어).

어떻 게든 is like 'somehow'. 거든 and 게든 are very similar. It means to add 'if' to the sentence. its not needed though because it is just add on word but you can use to make your sentence stronger. Sorry for bad english..>~<