Thanks for the help 
With your tips I succeded for changing the speed everytime when I pick up a coin. I also add the picture of the blueprint for people with the same problem. In the spawn point I also placed a collision box that sets the start speed add thousand. The * is used to ad 10 speed everytime I pick up a coin (I used a collusion box for begin overlap arround the static mesh to not let it mess with my destroy actor/sound on overlap with the static mesh) and the + is for the start value that has been entered at the start of the game.
