Is it ok to put the vias like that, help with something for a high current? The thickness of the route is 400 mil (200 on top and 200 on bottom). It is necessary to support ~15A. In the right corner the pad is smaller then the route, is that ok, i can put the vias in both sides? What helps if i put vias on the power routes and GND routes?
It is a good idea to do that, my recommendation would be for you to calculate the effective width of copper connecting layers in each via (perimeter of the hole * thickness of the plating) so that it matches a couple of times the width of the trace, make those holes as small as possible and put no more.
The reason for that is that if you put too many holes and those holes are big, then in the effective section of the trace in which you are placing them may be substantially reduced, there are other ways to avoid that like distributing the holes over a bigger area, yet you also want to keep them close to the connection point.