I have 5 Switches on a Private Network 10.0.0.0/8 with 8 Vlans. On Access ports is running Rapid STP. On Trunk Ports between Switches should i disable STP or not? I would be very pleased if someone can explain why.
You should not disable spanning tree on trunk interfaces. In fact, STP needs to be on links between the switches, which should be the trunk interfaces.
You can also leave STP enabled on the access interfaces to prevent loops if someone connects two access interfaces.
Look at it this way: if the links between the switches are not running STP, and somehow you have a loop, then your network will painfully die due to a broadcast storm. Recovering from a broadcast storm is not easy, and it usually involves shutting down switches or pulling connections until it stops, then you need to find the loop and break it before resuming normal operation.