'(These/Those/They) are our parents.'
私たちのです (watashitachi no desu) may be used to express '(This/That/It/They/He, etc) is/are ours' in the Japanese language. As the subject is often omitted in Japanese, the subject of this sentence depends on context.
'(Those/The) Two girls' parents'
It roughly means "Two girls and their Parents"
'(This/That/She) is my younger sister.'
'It is the second door on the left.'
'It is the first door on the right.'
"Shita" is a Japanese word and in English it means "Down"
Where's the bathroom.
"Watashitachi nani suru" translates to "What are we doing" in English.
I think you mean "genki desu ka". The correct way of spelling it in English would be "ogenki desu ka". It is Japanese for "How are you?" One would usually answer by saying "Genki desu. Anata wa?' which means "I'm fine, and you?"
"O-ai dekite ureshii desu" is a Japanese phrase and in English it means "Nice to meet you"
'The third number is 7.'