1)

first_side = int(input())

second_side = int(input())

def perimeter(first_side, second_side):

perimeter = (2 * first_side) + (2 * second_side)

return print(perimeter)

perimeter(first_side, second_side)

2) не понятно, что значит "иначе увеличьте". сделал так -

first_side = int(input())

second_side = int(input())

def perimeter(first_side, second_side):

perimeter = (2 * first_side) + (2 * second_side)

if perimeter > 50:

perimeter = perimeter / 2

else:

perimeter = perimeter * 2

return print(perimeter)

perimeter(first_side, second_side)