Brother printer not printing black anymore

I cleaned everything that was possible and even the maintenance] 4 which is really deep cleaning and when I do the test it's a bit better but after 4 pages it's back to the mess and in the forum I saw that many people are complaining about this but no effective solution has been reported unfortunately and that's why I asked for help thank you

Finally, while chatting online, I was given a solution that, after nearly a month, proved to be effective; the technicians had also told me that the print head was junk, and replacing it would cost 100 euros, but a site advised me to perform a technician maintenance, i.e., unplug the cord, and when plugging it back in, keep your finger pressed on the menu button until the screen displays "maintenance#4#". Then, with the up arrows, press until 7, then ok, then until 6 and ok, it indicates cleaning all. Press with the arrows until 3, then ok, and then with the right arrow just once, it will show black, and then press the mono arrow. When it's finished, using the up arrow, go twice to 9 (99) and ok, and the printer becomes normal again. At first, do the cycle several times; at the beginning, it will print only 2 or 3 sheets normally, and after about ten times it will be as if nothing had ever happened. If you need more information, don't hesitate to ask.