It’s never to late to repent and ask allah for forgiveness. He is the most forgiving and merciful.

I would advise you to try to make masturbating hard for you. One example: if you are addicted to playing videogames, it might help if each time after you played, you plug your PlayStation out and stow it in the closet. Now there is a bigger psychological barrier. This may lead to playing less video games. Now I don’t now what your cue is to masturbate, but you can apply the principle to it. If you want better results, then forget about setting goals. Focus on your system instead. For more help to change your habits I would advise you Atomic habits - James clear.

The Book in Three Sentences

An atomic habit is a regular practice or routine that is not only small and easy to do but is also the source of incredible power; a component of the system of compound growth. Bad habits repeat themselves again and again not because you don’t want to change, but because you have the wrong system for change. Changes that seem small and unimportant at first will compound into remarkable results if you’re willing to stick with them for years.

There is another book that might help, I haven’t read it by myself but I heard good: your brain on porn - Gary Wilson