Golfer2806

I am 71 and just been through a major body engine reconditioning. Had Chemotherapy and stem cell transplant to fix multiple Myeloma, with the treatment finishing in August. I continued playing golf during my treatment as best i could struggling along but not giving up. My fitness level has dropped drastically and l am looking for ideas to restart my fitness build up and drop my handicap. I play twice a week and my play is not bad but i struggle with fitness and when i come home i am all completely exhausted. So looking forward to some constructive ideas.