I need help big help with Microsoft word Problem?

I was working on a paper and all of the sadden it changed all of the letter to symbols symbols like this ü S8 ¼¶Ëz²;2»‡ 5F9ïÁ¶ Ç ÞD’z™ ¼Þ i really need to fix this can anyone help me plis very important very very