You need more time doing stretching every day. I recommend 1 hour per day.
You can split it up to like, 20 min x 3 times or, 30 minutes x 2 times. Increase the intensity as you progress. You need to stretch hard. When you get used to it you will be able to stretch harder and incorporate reverse Kegels. But don't injure yourself you need to increase the intensity exponentially and always go on how it feels in your shaft and inner penis. Use
hydrocortisone 1% in order for the skin on your penis to heal faster. Apply after your length sessions. If you have the money you can get the
MOS-RED | NIR INFRARED LIGHT this will shorten your healing time. There is lifetime warranty so there is no reason to get a similar light from somewhere else. MOS-RED is awesome, and I could not do the intensity I'm doing without it.
If you want to keep it simple and on the cheap you can do like I did it, and use an
interior car heater to blow warm air into your tissue during your sessions (before/during/after). A heating pad can also be good and it's less expensive to run. The warm-up and warm-down method you are currently using should work, as long as you keep the tissue warm before/during and after your stretching sessions. Warm tissue will be easier to stretch, and when you incorporate bundled stretches (you need to progress to this) it will be easier to bundle more.
You can also jump on 20:4 diet. That will create you to a fat burring machine.

I can guide you if you need support.
If you want to, I can create a program for you?
Manual stretches with "only" your hands works. You can at least get your
newbie gains of ~1 inch in length and when you need more intensity you can incorporate, a
Power Assist/
Broomstick and/or
LENGTHMASTER 3. But if you buy LENGHTMSATER 3 you can as well skip the step of getting the
Power Assist, since the
Power Assist is one part of the
LENGTHMASTER 3, that is the handle part.
You can work on length first if you want to, or both at the same time. But you need a penis pump to get the expansion that you are looking for when working on girth. Others above have mentioned that as well. Important is to have a clear structure of your program and write a logbook with pen and paper. You have a great goal I think. I believe you can get there in time.
But as I said before you need more stretching time and more intensity in your sessions.
Kind regards
@squirt_inducer_man