When you use apps on your phone, various data is stored temporarily in the phone memory. If your phone runs out of memory, it may help deleting this data.
Slide two fingers downwards starting from the top of the screen.
Press the settings icon.
Press See all apps.
Press the required app.
Press Storage and cache.
Press Clear cache.
Slide your finger upwards starting from the bottom of the screen to return to the home screen.