I have to do this for school project.

Describe simple database, with at least 6 tables, at least one one-to-many realtion and at least one many-to-many realtion.

Basiclym I nead some sort of diagram with tables, table fields and relations. It has to be something related with transport or traffic.

Ideas, anyone?

yes
why not try and think up an example of your own.
come back here if you are struggling
but at least make an effort to do your own coursework, before looking for help

i have something about public transit bus system.

Tables would be vehicles, garages, drivers, bus lines and one table which connects vehicles, drivers, and bus lines.
Garage - vehicle is one-to-many,
vehicle - bus lines is many-to many, etc.

I need one more table, and I cant think of anything else.

fares?
stops?
routes?
schedules?