Testostrone

Hey I’m a 50 yo male. I’ve worked out most of my life on and off. I have a little fat around the middle but decent shape. My doctor has tested me and been told my test levels were low. So I elected to have a testosterone implant. I feel the best I’ve felt in years. I’m just wondering how much this will help me to build muscle at my age ? Before it seemed nearly impossible to gain muscle size. I was told my test levels are at the range of a 25 yo.