Hi everyone! Please, what safe potent ingredients can I add to a face lotion I'm making for myself, for my face to go three to four shades lighter within seven days?

NONE!!
None none none
There a countless products, but they either don't work or do damage, for lots of money.
I'll bet you are beautiful - deep sparkling dark eyes, shining lustrous hair, white teeth when you smile.

I'm very fair. I now have skin damage and skin cancer, little red veins in my face, pale eyes and eyelashes that you can't even see.
Be glad for your dark face.

White women use tanning beds and spend long hours in the sun to get dark. Trump uses tanning sprays that turn his skin orange. Too many of them will end up with skin cancer. My former sil used to sunbathe often and had a gorgeous tan. Today, at the age of 73, she is one big ugly wrinkle and has damaged skin.

Like joypulv said, take joy in your dark beauty. An added plus is that you won't age badly and, when you are old, will look much younger than you are.

Use a daily facial scrub to exfoliate and generate new skin. Always use a lotion with a high spf to prevent further tanning.

There is nothing that will get you 3-4 shades lighter within that time frame - anything with bleach or harsh chemicals should be avoided as it can cause hyperpigmentation and make problems worse.