Has anyone used testosterone injections? What were the results?

For context, 35 year old male. Have had / "Low" testosterone for as long as Ive been an adult. Always had problems losing weight, building muscle, getting proper sleep, and generally low sex drive. Also have a slight case of gynecomastia. Sleep schedule may be due to my job and stress, but I've heard hormone levels also could play a part in that.

After getting some blood work done, it shows my levels are 296 ng/dl, whatever that means. It also says the normal range is 249-836. Obviously it's within range, but on the very low end.

My doctor did say that he could prescribe some injections, but ive never dealt with this before. What kind of side effects would I expect? Would this help with the weight loss/muscle gain (assuming I'm putting in the effort in the kitchen and gym as well)? Would it help or worse the gyno? Is this a life long thing, or just for a few months/years? I'm sure a lot of these are rookie questions, so appreciate the patience. Just trying to do some research and ask the people who have been in similar situations what should be expected, so I can weigh the options of whether I should try it out, or if I'm better off just staying as is.

Thank you