Hello indrit208,
Thanks for reaching out in Apple Support Communities. We understand that you're having trouble with your iPhone's keyboard, it disappears. We're happy to help. Before attempting any type of reset, make sure you have a current backup. Have you tried restarting your iPhone? A restart can help to refresh the OS and connections. Do you have any third-party keyboards installed? This can help us to narrow down the cause of this issue.
Check out the following support articles:
Restart your iPhone
How to force an app to close on your iPhone, iPad, or iPod touch
Cheers!