Of course, 3 meters is enough, even if it’s not exactly comfortable.
But honestly: a 15-meter narrow plot requires, in my opinion, a bit more individual planning than a standard villa with garages on the left and right.
You can possibly place the garages in front of the building, which has the advantage that you can still walk around the building.
But that depends on the location and development plan, how you do what.
Regards
Of course, you can’t build with a cookie-cutter plan under such conditions, but the OP is rather reserved regarding information.
For example, I could also imagine a partial integration of the garage into the main house, but then you lack the available budget, site plan, etc.
You don’t just need two garages, but also two driveways, two gates with motors, electrical work twice...