Have patience because hair is dead, it took a long time for it to get damaged and it will take time for it to improve.
Just keep doing both protein and coconut oil treatments regularly, you will only get a certain amount of penetration and adherence each time. Then whenever you wash your hair some of the protein and fatty acids are removed, there is no way to make it stay in or on the hair permanently, that is why we are best not to limit damage, aiming to retain our natural fatty acids and proteins which are bonded to the hair.
Heat and a longer timescale may help a little more penetrate but it will not help more adhere to the surface once all the damage is patched. You can also use a protein rich leave in conditioner, work with your hair properties when you select ingredients - make every product work for you.
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
CO-wash: Inecto coconut
Treatments: Komaza Matani, coconut oil, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume, Inecto argan
Styler: Umberto Giannini jelly, Boots Essentials gel
Experimenting with: going back to basics