Hey davitpapikyan,
Thank you for using Apple Support Communities!
If we understand correctly from your post, your user photo becomes blurry after turning on your Mac to login. We can help.
Try these steps to test from Change a user’s picture on Mac:
Use a picture included with macOS: Click Defaults, then select a picture.
Take your picture using your Mac: Click Camera; when you’re ready, click Take Photo.
Use a picture from the Photos app: Click Photos. To see specific photos from a time, place, or album, click a disclosure triangle below photos, then select a group of photos. Select a picture, then click Next.
Use a picture from the Photo Booth app: Click Photo Booth to see pictures you’ve taken using your Mac and the Photo Booth app. Select a picture, then click Next.
If you're still having issues, try the steps below:
Make a test user account along to isolate the account itself as well as resetting the NVRAM:
How to test an issue in another user account on your Mac
Reset NVRAM or PRAM on your Mac
Cheers!