A function is a rule that assigns to each element of a set called domain a unique element of another set called codomain. So, the way you can figure out if this is a function is by checking if every element in the column x has a unique element in the column y, that is, if the elements in the column x does not repeat. Since this is the case for your question, then it is a unction.
To know if it is proportional you have to make the quotient y/x for every row, 16/-3 = -5.333, 11/-2 = -5.5, etc. If this whas proportional, then every quotient should be equal, but this is not the case (notice that -5.33 is not equal to -5.5), then it is not proportional