Yes 240C is good for the build, 220C will work but not as strong. 260C is the point where you start to get colour changes.
The first layer of the raft and the first layer of the object need to be at lower temperatures so that you separate the object from the raft and remove the raft from the bed.
I do the first layer of the raft at 225C onto Foamex board. Most people use an Acrylic bed which may require a different temperature. Best to start low and move up in 10C increments until it sticks enough otherwise you can ruin the bed.
After making the raft I cool it with a fan for a couple of minutes to ensure it is back to room temperature. I then do the first outline of the object at 215 and the first layer infill at 195. That makes the raft peel-able. I think other people raise the height of the first layer and do it at the same temp as the rest of the object. That leads to an untidy underside because the bottom layer filaments are not squashed together enough.
If you can get hold of PLA I would recommend starting with that as things are much simpler. You don't need a raft. The bed material is just covered with blue masking tape. I do the first outline at 210C and the rest at 190C.
PLA is a bit more difficult to extrude though because it softens at 50C, so if heat spreads up your extruder's insulator it can form a long plug that causes a jam.
Note that all these temperatures are measured at the heater. If your thermistor is mounted somewhere else it might read up to 20C low.