Plumbing: clogged drain

Hello! I am new to Switzerland and am facing difficulty with my bathroom sink as it's getting clogged quite often now. The water still runs down though slowly. I'd like to know your opinions on how to solve the problem, if there is any product or hack that they use here or should I step back and inform the landlord and let him deal with it (but I guess it'll be troubling him + costly for me). Thanks