As we dont have any polish language learning institution here, beside that which european language do you suggest ??( french, germany ??)
Unless you're talented language learner you won't learn good enough foreign language in 2-3 years.
According to this website salaries are according to language popularity:
Popular and less payed: German, Romance
Not popular, so payed little more than previous: Hungarian, Norwegian
The most payed: Finnish, Hebrew
Arising growing numbers Shared Services Centers in Poland provide employment to many people with higher education. In addition to a master's degree are also counted interpersonal skills and languages knowledge. The more they are niche, the candidate can earn more. Specialist familiar with Finnish language will earn even 7.5 thousand zł gross, and the manager with the Hebrew 12 thousand zł gross.
Shared Services Centers is a separate organizational unit in which the services are provided (accounting, IT, payroll, personnel, etc.) for internal clients. This brings many benefits to businesses, among others eliminates duplicated implementation of activities in many places, reduces operating costs, increases efficiency of administration and improves the specialization. For us, this means more jobs and opportunities for development in an international corporation.