My testosterone levels(free and total) were low. after treatment levels are normal. how long will it take for symptoms to go away like bad memory

Nothing to do: Don't believe bad memory is part of the low T problem. It is also unusual for someone at your age to have low T. You will have to look elsewhere for your bad memory.

I don't know what...: ...other symptoms you had before starting the testosterone, but low testosterone levels shouldn't affect your memory. As such I wouldn't expect your bad memory to improve once your testosterone levels have returned to normal. You should talk to your doctor about the memory problem.