You dont ask for a raise. You get exactly what you deserve. Hear me out: No one ever gets a raise before they start doing the extra work. It is always a case of "wow, we better give Alice a raise since she's doing so much and it would suck to try and replace her with someone else at her current pay".
The OP specifically said that he feels like leading the projects and adding a lot of value. 32k in euros before taxes is awful. No one will give you anything unless you ask for it. Exploiting VISA workers is a common thing - he is afraid he is being exploited.
It is always a case of "wow, Alice is working like a superwoman for that shitty salary, thank God we have her on the team, because other people would have been a lot more expensive".