Hi there. I'm so sorry that your friend is having difficulties. I don't know anything about the health care system in Malta, but I do know that developing psychosis is not a good sign. Please find out what medications have worked in the past and write them down on a list. Also make a list of all the medications that do NOT work. Also make sure your friend is not abusing or using any non prescription drugs, and is taking any prescribed drugs correctly. Both instances could cause psychosis to develop, and the treatment would be very different than if he didn't have any drugs in his system. If he is still coherent and is able to make his own choices, then the best you can do is persuade him to go with you to get medical care. Bring the information about his medication history with you to that appointment. However, if he is unable to make decisions on his own, especially if he is doing anything that could potentially harm himself or others, you do have the option of getting authorities involved against his will in order to avoid injury or harm.
I'm sorry that this is such a difficult situation for you. Try your best to talk calmly and reasonably with him, present his options in a calm voice, and be rather forceful with any doctors he sees in order to get a prescription for medication that has worked in the past.
Best Wishes and good luck with this very difficult and concerning situation.