Eventually. Untreated lymphoma will kill you. Different kinds of lymphoma carry different prognosis and may be more amenable to treatment than others.
Not in many cases. There are more than 30 kinds of lymphomas. Some of them are very aggressive, others are not, some of them are highly curable with chemoimmunotherapy, some are not curable but most patients live with it for many years. Find a major university or institute and get a good opinion and diagnosis. A in-depth care plan then can be crafted for your your medical oncologist.
There's hope. I will assume the diagnosis is correct. Untreated, malignant lymphoma is fatal. Nowadays, we cure many of these -- it depends largely on the type. You must opt for scientific treatment and avoid hucksters -- people offering "alternative" cures are your worst enemies. Remember that nothing you did caused your illness. Good luck.