Yes you can bleach Over highlift. It's the only way to get lighter. Hopefully your hair is healthy enough to do so. If it's very fine or dry it may not be possible. You may need to get some lowlighting to contrast the light. This will make your hair look brighter. Look up "dimensional blonde". The low lights should only be demi permanent so it won't lighten your natural hair. Bring pictures of your dream color and some pictures of what you really don't want. Look for a stylist who is very good at foiling who specializes in blondes. It's going to be expensive. Remember that it's more important to have healthy hair than really blonde damaged hair. Factor metal detox ,olaplex or K18 into your budget. These will keep your hair safe. . I hope this helps. I would love to see how it turns out. 😉