I am doing my internship at a German company (while being a student from the Netherlands) and my German skills are limited. On sunny days, I get blinded by the sun and want to lower the window blinds. I have an older coworker in the same office, whom I do not talk to much (he doesn't speak English and besides, there is quite an age gap). To be polite, I always ask him in German if its okay for him if I lower the window blinds. Note that he does not need the blinds himeself since he is not in front of the window.
Everytime he simply answers with 'Ja, ja', or yes, yes in English. I have been asking him this question for the past two weeks and he has never objected to it. Can I assume by now that he will be fine with it the next time I want the blinds to be lowered? Or should I keep on asking if he is okay with me doing so ('just' to be polite)?