- the files cannot be deleted also using filezilla and ssh connection
- it shows only read permissions
- i tryed to change some configuration, but after restart everrything is lost
- also reset configuration didnt helped...

Looks like your flash is mounted read-only for some reason. Maybe it's failing. You could try a netinstall; if that doesn't fix it, you're probably out of luck.

I solved it connecting disk from routeros to linux machine using usb, deleted file routeros v7.npk with 0b size and after that it runs, also there is configuration I installed before this problems