Pi4 Parallel64 not working || Mupen64plus FPS problem?

Hey guys, i hope someone can help me… I am new to Lakka. I recently bought an Pi 4 for retrogaming. Its the 4GB version and its overclocked to 2Ghz and 750Mhz gpu.

Now my problem is that when, as example i run Super Mario Kart 64 with Mupen64plus, i only got ~25 FPS, even if i change the game settings to fullspeed. When i try the Parallel64 Core, none of my games started with it. I get an blackscreen with restart to the XMB.

Does anyone have any suggestions to me ?