I have recently recovered from the same issue. But mine was worse. I went from blonde to dark, then blonde, then dark, ugh! You have no idea.
My hair is in pretty good nick now and it’s only a few months. Here are the remedies I tried.
mayonnaise pack. Yes just normal mayonnaise from your fridge. Comb through and leave on for about an hour. Cover the head with a heated towel, you can do this by putting in the micro wave (damp) and keep reheating.
Have a good trim, you may have to go a fair bit shorter, but the trim will really help and your hair will grow better anyway.
Take a vitamin with biotin daily.
Try where you can to let your hair dry naturally. If you still need a hair dryer use heat protector products.
Deep condition with a moisture pack twice a week.
Get some shine products that cover the hair shaft with a sheen, it helps to make hair look better and evens out cuticles.
I find M label has a great shine shampoo which also makes hair look healthier.
After a month or so, you can have it coloured again to deal with the red colour you have now, but ask the hairdresser to use none damaging pigment colours like a brown colour rinse. As the red colour is a dead give away for hair that has not been coloured correctly.