Ginge das?
I assume it means „is this possible“
What is the grammatical case here? What is the verb stem?
Thank you in advance!

Question

Ginge das?
I assume it means „is this possible“ 
What is the grammatical case here? What is the verb stem?
Thank you in advance!

Answer

"Ginge" is the Konjunktiv 2 form of "gehen". It is build from the past tense (Präteritum) stem, which is "ging". 
The translation is something like: "Would this work?" or "Would this be ok?"