"与"means "and",For example: u and me are plying basketball.means do sth together with sb '于"means" so " ,example i'm hungry so i need sth to eat 予means " give" same with 给，they were a phrase:给予，in chinese we read it:jiyv . 余means :"the remaining",example if i have three apples and i ate two of them minutes latter ,now the last is the remaining apple . 於=于 the former was a complex characters with the latter in chinese, but they are the same meaning . is that aright?