Hi @polinaaleksandrovna9, I am sorry to hear about this.
I have translated your question to English as this is an International forum, please post any replies in English and it will be easier for me and other users to assist you.
Have you tried clearing data for the camera app? This will not erase any previously taken pictures or videos, but it will reset all settings for the camera app which might do the trick. In order to do this, find and tap Settings > Apps > Camera > Storage > Clear data > Tap "OK" > Restart the phone.
Another thing you can try is to restart your phone in safe mode in order to see if the camera behaves the same there. All apps downloaded from Play Store is temporarily deactivated while in safe mode and by doing this, you can see if this behaviour is caused by a downloaded app. For more information on safe mode and how to use it, click here.
If none of these measures manages to improve the functionality of the camera app, I suggest that you try to perform a software repair using a computer and Xperia Companion. Keep in mind though that a software repair will erase all user data, so remember to do a backup of your user data first.
Try these measures and let me know how it goes!
