Thank you all guys!
Yes, it is indeed a wonderful thing to save an old camera from the trash.
So far, the areas that need to be worked on I discovered are:

- Patch the bellows
- Paint the bellows
- Glue the leatherette
- Paint the leatherette
- Get rid of rust
- Shine the metallic parts
- Clean the outside glass
- Clear fungus
- Clean the inside glass
- Unstuck, lubricate the mechanics

Do you have tips regarding the methods, tools and liquids for them?