I have problems with memory, maybe virus or something

Do a forced restart for your phone following the steps below.

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

Then see if this helps.

https://www.anysoftwaretools.com/fix-iphone-storage-almost-full/

If not, consider doing a restore via iTunes and see if that fixes the problem.

Unless you have a jailbroken phone you do not have a virus.

Go to Settings-General and scroll to iPhone Strorage to see what is using the phone's capacity.