It is strongly not recommended to treat someone without experience in other disciplines, you will harm yourself. The main mistake of beginners is to use their own Powers and Aura to treat others, which binds them to the patient's disease and negativity, and as a result you two will end up on the bed together. Of course, the disease will not recede in the patient. This is not the kind of Knowledge that is taught in a day/month/year. You can learn only the basics in a few years.
The danger is that you potentially link yourself to the Karma and negativity of the person, in which case it can transfer to you and affect your Karma. Healing others is always a very sensitive process that requires Mastery. Can a person heal someone if they themselves are in need of healing? Think about this and put all your energies into your own Spiritual Elevation. The person you describe has his own Table of Destiny. A person initiated in the Occult Sciences and who understands the principles of Healing would not ask such questions as you do. Hence, you do not understand the depth of the problem.
You see, a person will not be completely free from Karma, even if you manage to help him but only temporary corrections are made. Such diseases connected with Karma always come back because their root is in the deep Programming of the Human Essence, which even if controlled in a safe state, is controlled by discipline in effective measures of health control and constant, otherwise there will be a setback again and the disease will progress, or complete Freedom will be achieved through the Purification of the Soul, its Freeing. One must be diligent in working on oneself. And it should be done by the one who has such problems, not by you.
You can accurately direct your friend to Satan, open to him new facets of Being, give him Knowledge and tools that will allow him to improve himself. This you can do. But otherwise I do not advise you to take responsibility for someone's life, especially if it is accompanied by objective dangers for you personally.