Verified answer

shave it off and start again.

Wait for grow

You'll have to grow it out

grow it out-will take a while

you're going to have to wait for it to grow back

See a professional colorist. It's not going to be cheap. With any hope, you have learned not to muck around with diy 'remedies.' They rarely work.

You need to go to a hair dresser. Dirty blondes tend to have natural hair darken with age at the roots, but then hair naturally lightens from the sun...so it constantly looks like it’s ‘dirty’, lol. Once your natural hair is back, get highlights every three to four months, that will even out the tone and get rid of the red or yellow undertones.

Dye it back close to your hair's natural colour or let it grow out.

Maybe use some uncolor.