you can save multiple variables in sequence like
f.store_string(my_string)
f.store_8(my_byte)
f.store_16(my_word)
and you should read them exactly in that order too!
or you can store a dictionary like json string
f.store_string(my_dict.to_json())
and read it like
var my_dict = {}
my_dict.parse_json(f.get_string())