Is there any way to fix VLC video player because every video I watch with it is always fragmented every 10 seconds?

NOTHING WRONG WITH VLC PLAYER, IT IS YOUR COMPUTER IS TOO SLOW OR RUNNING OUT OF RAM.

VLC has a **** ton of keyboard shortcuts that do every sort of thing, so you probably hit one

id reset VLC to default settings;

If you installed VLC properly you can delete the preferences and cache by simply opening the shortcut you can find in your start menu:

All programs > VideoLAN > Reset VLC media player preferences and cache files

Deleting the files manually

Open the explorer and type %APPDATA% into the address bar and hit enter. This should lead you to the AppData folder of your user.

Therein you should find a folder named vlc. Delete that folder and you're done.