I have thick dark hair naturally too. Here is a photo of my natural color (it’s been straightened and blown dry in this photo). Obviously the ombre is not naturally part of my hair… the brown is my roots.
I was pastel pink/white blonde for a short while in between purple and green, here is a photo of me, a super dark brunette gone blonde.
See, it’s possible to have really dark hair naturally but look good blonde. BUT, it won’t be the same after. You need to pamper your hair with conditioners, serums, etc. It might take you several bleaches to get it where you want. I recommend going to a salon since you’ve likely never changed your hair color before, and also it will help prevent extreme damage.
There is no ‘safe’ way to bleach your hair to maintain health. This is such a common question but like, gurl, no, of course it’s not going to be the same! Think about it: you’re stripping the pigmentation from the follicle, and the nutrients and oils with it. It’s never going to be the same. That is just wishful thinking. I don’t think bleaching yr hair is a bad idea, it’s your choice, it’s just that some hair can withstand more damage than others and it might take a long time (and a lot of money, even if you do it at home) to lighten up so many levels. It’s not a weekend job, not if you want it to turn out nicely. This is a sacrifice you have to consider when it comes to lightening hair color, especially such a drastic change. You can pamper it with lots of products to get health back into your hair but the post-color process is a lot more intensive and typically more expensive.
I did a video for rookie on how to bleach your hair here, and there are plenty of videos also on youtube, and we have a recommendations and hair tag also. I deleted my other tumblr which housed my Hair FAQ else I would link to that also, but oh well. Hope this helps.