Are there opportunities? Any tip and advice is welcome

You might have a better chance if you worked for a German company that would put you on a temporary posting in Vietnam.  I had a private at-home student who worked in corporate training at Bayer.  He was close enough to the top that he met maybe weekly with the German country head using English to communicate.  At your educational level you would be competing for direct hire with college educated, English speaking locals.

I have read elsewhere, and observed in other postings here, that Common Market countries tend to move people into many technical and non-management white collar occupations with advanced vocational training rather than academic degrees.  In fact, many are now advocating the same for the US.  The problem for such Europeans is that Vietnam is using the university model for credentialing.  In fact, I believe that Vietnam has more people with Bachelors degrees than the economy can fully absorb.