Xbox Game Pass Ultimate vs. existing subscription Xbox Live Gold

Hello,

First - im writing from Poland and my topics is about offer in my country. I have active subscription Xbox Live Gold. Recently in store shows up an special offer - 2 months Xbox Game Ultimate for 8 PLN (about 2$). I want to buy it but I'm not certains what
happens:

1) With my current, active subscription Xbox Live Gold

2) With my active subscription Xbox Live Gold after 2 months, when Xbox Ultimate will expire.

I'm even be willing to convert my curent subscription to Ultimate but dont know the conversion ratio (my subs will expire 26 januar 2020)

Please help.



:)