I work on a website that has different language interfaces, so far I use english and german.
when the german text is loaded, it shows weird characters like the following screenshot

though I use
header('Content-type: text/html; charset=utf-8');
and also in the html header
<META http-equiv="content-type" content="text/html; charset=utf-8">
what else can I do to solve it ?
Thanks
The content of the page needs to also be in UTF-8. Your content was probably made using MS Word, which uses Windows 1251 encoding. You need to re-save your document as UTF-8.
UTF-8 does not convert formats for you.