How I can remove the connections in the uv-map?

May as well tell you now that the polycount is high. It would be best to try to reduce it. Decimate will ruin your topology so I prefer to dissolve edges. If your faces are in tris press T to open the side panel then use alt+J to turn the faces to quads. In the side panel, put a checkmark next to compare UVs so your UV layout doesn't get messed up. Edge select mode. Hold alt to select entire edge loops and shift+alt to select multiple edge loops. Then press X > dissolve edges. You could most likely dissolve every other edge loop without changing the shape of your mesh.