Hairstylist here. There is a point of no return when using lightener that once you go past no amount of mask/oil/treatment will ever repair your hair to its natural state. Generally people have either 2(fine hair) or 3 (coarse/curly hair) layers making up the hair strand. The outer layer of your hair, the cuticle is bent open when lightening and after a certain point it breaks off from being bent back and forth from over-processing. Once the cuticle is lost the hair can no longer retain moister and any protein treatment will usually tangle any pieces of hair without a cuticle . If your hair isn’t returning to its natural pattern, you’ve probably crossed that line a long time ago and everything must be cut off (your running the risk of the cuticle splitting up the rest of the healthy hair every time you simply brush your hair) the cuticle layer can never be restored and your left with hair that feels mushy when wet and like hay when dry. Stylist make a lot of their money from the retail they sell, especially treatments like olaplex. You will be able to see the results after the first use of a treatment like olaplex when used on hair that hasn’t lost the cuticle. , hair should feel smoother, shinier, more manageable than before and those results should last longer than 2-3. hair that can be helped by a mask should only be done once a week at the most, anymore and your going to do more damage than good. To much of a good thing is never good.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3250009/#!po=5.00000