Using an abbreviation of another language in the abstract I'm writing the abstract of my bachelor’s thesis and need to refer to a German research project. The abbreviation of it refers to a German spelling – so I can’t write it out. The English translation wouldn’t explain the acronym and is super long.
Is it possible to use a footnote for this? Even though it is very uncommon? Or are there other possibilities?
I don't have strict rules to follow but generally APA as guidelines.

The exact abbreviation I refer to is STEER which stands for Erhöhung der STEuerungskompetenz zur ERreichung der Ziele eines integrierten Wassermanagements.
In English: Increasing Good Governance for Achieving the Objectives of Integrated Water Resources Management.
You could refer to the German research project by acronym without referring to the full name or you could omit the acronym entirely. The former is perhaps better when the acronym is well known; the latter when it isn't. Since you'll surely be providing the full name, acronym, and translation later, either should be fine. 

I suggest that a footnote be avoided, because abstracts get decoupled and such a footnote will be lost.

Given that 


  STEER: Erhöhung der STEuerungskompetenz zur ERreichung der Ziele eines integrierten Wassermanagements (Increasing Good Governance for Achieving the Objectives of Integrated Water Resources Management)


isn't particularly long, you could just include, assuming your abstract isn't limited by a word count.