Aren't you scared about loosing your data?

No. I still have files from 1991. I've got files that have migrated from floppy disk to hard drive to QIC-80 tape to PD (Phase Change) optical disk to CD-RW to DVD+RW and now back to hard drives.

What if I get a ransomwarei don't realize and all my backups get encrypted too?

Then you need to detect the ransomware before you backup. I use rsync --dry-run and look at what WOULD change before I run it for real. If I see thousands of files change that I did not expect then I would not run the backup and investigate what changed before running the rsync command for real.

Or if the backups are corrupted

I have 3 copies of my data. Local file server, local backup, remote file server.

I also run rsnapshot on /home every hour to another drive in the machine. I also run snapraid sync to dual parity drives in the system once a day.

I generate and compare stored file checksums twice a year across all 3 copies to detect any corruption. Over 300TB I have about 1 failed checksum every 2 years.

and my disks breaks?

If one of my disks breaks I buy a new one and restore from backups.

But also I'm afraid about cloud

I don't use any cloud services because I don't trust them.