There seems to be another problem now. When I change the output on one track to master. It somehow affects the other tracks too...... x_x
Where do you have them routed to and where do you want them routed to?
FYI, the norm for a really simple mix is to have everything routed to the Master out. As things get more complicated, the next most common routing is to send some of your tracks to Groups (so you can process/add effects to multiple tracks at once) and then route the groups to the master. For example, you might have a Drum group, a Backing Vocal group and so on--but to be in your final mix eventually everything has to go the the Master, either direct or via a group.
The third example of routing is, if you own a hardware mixer and multitrack sound card, you can send individual tracks to individual outputs.
However, in none of these cases should changing the destination of one track affect change the routing on others unless you have some sort of strange loop created.
Maybe a screen grab showing the appropriate part of the screen so we can see what you have set up?
Failing that, unless you've gone too far down this mix, maybe start from scratch with the New/Session menu?
Finally, if you work on a lot of similar projects, don't forget that you can can create a new session then same it as a session template before you add any files--including your pre-selected routings and stereo/mono designations for tracks.