Thanks all of you for the answers.
As for Davidw's answer, I would like to ask what soldering iron model and what other stuff I should buy if I wanted to open the laptop and fix this jack?
Moreover, I would like to ask you why you Davidw's mentioned that replacing the jack for a new one would be needed? Would not be enought just to resolder the jack which has become loose? In case I had to buy a new jack, what kind of shop could sell me this kind of jack? I am not sure whether typical computers shops sell this kind of jack or not.
In-home technical services for computers to individuals and small companies. Arganda, Madrid, Spain