My phone deletes or destroys pictures, is that a virus and how will I get rid of it?

Some time ago, I noticed for the first time that pictures of my phone just disappeared. I did not think about anything else, I thought I might have deleted it and would not remember it.

Then every few weeks all songs disappeared. The problem I have not since I download it on the laptop and then pull it by cable to the phone.

For about three months now, my photos and WhatsApp images have not really disappeared, but they no longer have a thumbnail image in the gallery and can't be opened in any other way. This sometimes happens right after a picture has been taken. Screenshots are deleted so fast that I can't even send them before. The pictures that are sent to me on WhatsApp, are there after about 5 minutes only to see pixelated, so I can see nothing.

In addition, the phone has become relatively slow, the camera takes a long time to open and I'm sometimes not longer in my phone, because the points for pattern input not open.

I think I probably have a virus. Therefore my questions:

Is it really a virus?

Is there a way to get rid of it?

Is it worth it to buy a new phone or can the virus be on the SIM card or the SD card?

Is there a good free virus program that I can avoid in the future?

Thank you very much, because you have read this long question,

Your Beehappy

Get a virus scanner

Do you have a cleaner app on your phone?

Yes, it does not help