When brightness increase screen start blinking

@jatinkumar94327 sounds like a bad display that is losing it's backlight. I'd start off by replacing the display and then re-evaluate this. If it still doe this with a new screen, the issue is most likely going to be on the circuit board. The backlight circuitry maybe having bad components etc. For that you will need to have the schematic, the component layout drawing as well as the right tools to diagnose this. Again, start with a new screen. That will give you a known-well starting point for any further troubleshooting, if necessary.

To replace the display, and since iFixit does not yet have a specific guide for that, use this one It is written in Spanish so use a browser that will do the translating for you, if needed.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has the same issues with their device. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!