To be honest, it’s a bit late to learn another language now. If you work in a profession, you will be too busy to have time to learn a language again.
Patent documents involve a lot of professional terms and involve laws, so the accuracy of the translation is relatively high.
My personal suggestion is to learn English well first and then consider a second foreign language.
If you have a basic knowledge of a small language, you can continue your studies or even give up English. There is still a market for agents working in small languages.