QUESTION: Fix punctuation: Potassium is one of the salts that together with sodium is lost via the stools
ANS: Potassium is one of the salts that together with sodium is lost via the stools.

QUESTION: Fix punctuation: Therefore they choose to have their packaging and products made of FSCcertified paper and printed with water colours
ANS: Therefore, they choose to have their packaging and products made of FSC-certified paper and printed with water colours.

QUESTION: Fix punctuation: Upon receiving the apartment keys you will be asked to pay a deposit of 2490
ANS: Upon receiving the apartment keys you will be asked to pay a deposit of 2490.

QUESTION: Fix punctuation: I am Veronika from Kiev Ukraine
ANS:
I am Veronika from Kiev, Ukraine.