Sen bendensin ne anlam tasiyor?

in a restaurant/shop store : I also pay instead of you.

about an idea: You think like me./Your idea is similiar to/the same as mine.

Or, possibly, "you´re in my house/at my place".

ben+de(locative)+sin--->bendesin (direct: you are at me) usually means : you are in my house

İki hafta bendesin. (You are/will be at me for two weeks.) is understood "you will stay for two weeks at my home."

biz (we)

biz+den(ablative)+sin

Sen de bizdensin. (You are one of us, too. (direct: You are from us, too.))

may mean according to the situations: a) You are in the same idea as us. b) You are belonged to our group. c) We´ll pay instead of you too. etc.

biz+de+sin---------->bizdesin (you are at us)

Annenle babandan izin aldık, bu hafta sonu bizdesin. (We got permit of your mother and father, you will stay at our home on this weekend.) (direct: We took the permission from your mother and mother, you are at us on this weekend.)

thank you all very much!