Hello @Thoon_Aung and welcome to the forum 
Which version of Windows are you using?
It looks like you’re using a 5.2.0-beta release there. Did you have that problem with version 5.1.5?
If not, you need to report this in the 5.2.0 testing topic.
The 5.2 Release candidate is now available:
Krita 5.2 Release Candidate is out! Please help us in another round of testing!
If you’re not using the 5.2. release candidate, please try that to see if the problem still exists there.
Please make any problem report in the 5.2 release candidate topic.
Hello @Michelist