If I update 8.1 to windows 10 will I loose any data?!

I updated to Windows 10 on two devices and didn't lose any data, pictures or anything else BUT you need to keep everything backed up on external storage whether you update or not.

You should keep all your personal data. Pictures, videos, documents, etc. So, you shouldn't, but can't guarantee it.

If all goes well then you shouldn't. but you should back up your data in case it doesn't go well

i didnt

You should be fine. I store everything also on either OneDrive or DropBox for backup.

If I could go back I would never do Windows 10. I just dont like it.