utf8_encode problem

I have a file need for german language. I use utf8_encode that my site can view character like ö and other, which not the usual letter.
Everything is fine. But there's something bother me.
for example, the text is Überprüfung
When, i try to access the file, the unique character is change to like this: Ã^Überprüfung, even i have input the text: Überprüfung
so, i have to use utf8_decode to fix that.

But at the other file, the text i input doesn't change. It keep written: Überprüfung
I don't know what happen. I try at the localhost and my VPS and both get the same result.
Any one could give me solution please?

Thanks