You have friends here. Online friends, but we are all real people behind all the written words. You can get new close friends as you continue writing. Interacting on the site.
I wish I could rewind my time too. But it can't be done. The best you can do is look around where you stand today. Where do you want to go? What are your goals and your dreams? Aim for your dreams. The path won't be smooth and straight, but keep your head up and keep aiming for your dreams.
If you look behind, see how far you have come. Looking back won't tell you how much is left, it will only tell you your history. You can't aim for what has been because time goes forward. If you keep looking back, you will stay where you are.
Not saying you need to forget your past, in your past you have knowledge and learning.
About your best friend's death. Maybe you need therapy to over come the sorrow. Not to forget her, just to handle your sorrow. I have several relatives and friends who have passed away. If you get stuck in sorrow, you need help to get through it.
Tony