Fix Tags (hreflang, canonical...) in website

I have web site address which has error's in hreflang, canonical, Open Graph tags... Site is multilanguage: serbian, english and german. I am looking someone who has experience in building and setting multilingual site and who can fix this error's and optimize our code. Google has excluded a lot of our pages (duplicates, not selected as canonical), so this errors must be fixed also. Priority is Serbian language.

In attachment in pdf file there are more details about job.