Hey riyaz3222,
Thanks for using Apple Support Communities! I understand you're experiencing an issue with part of your keyboard. I definitely want to make sure you're able to utilize your entire keyboard, and I'm happy to help.
I recommend taking a look at the resource below and working through the steps there under "If your display doesn't respond to touch".
Get help with the display on your iPhone, iPad, or iPod touch
If those steps don't help, let us know a but more about what's happening. Some helpful information would be:
Does this happen in all apps that use the keyboard, or only some?
Do you have multiple keyboards installed? If so, does this behavior happen with all keyboards?
Thanks again, and have a great day!