Is there such a software that allows you to enter different passwords. When you login with one of them you can see all your files, but when you put in the another one, you can only view selected files?
You should elaborate on you true intentions. If you are trying to setup a local file share that you can edit and others can read then simply set the permissions of those files to readonly for others. If you are setting up an online file share like Dropbox then the process is the same.
What about using something like TrueCrypt? Don't know if this exists for Ubuntu and yeah, I heard that they stopped developing and say they are not 100% safe anymore, but if you don't have to hide things from the FBI/... this is more than enough. You can create virtal volumes that you save either as a file on your disk (you can also hide it e.g. in a video file) or in unpartitioned space on your disk. Any encrypted data created by TrueCrypt should theoretically look like random numbers and therefore your boss or anybody should not be able to see even IF you have encrypted data. But I don't know if it only exists (existed) for Windiws, though...
Is there a software that allows users to have different passwords?
When you login with one of them you can see all your files, but when you put in the another one, you can only view selected files?
No, never going to be possible. You need 2 users for this with each their own password where user2 only has access to part of the files of user1. This is actually very typical of large organisations where individual users have access only to the information they need on a file server.
To accomplish this you need to set up a data directory (or data partition if you'll be adding more users afterwards) using groups where individual groups have access to certain directories.
If you want to "hide" just one particular directory or a bunch of files from another user (like dad) that has access to your password , just look at this answer: How can I easily encrypt a file?