Hello @sv and welcome to the RobotShop community!
I haven’t worked with the Lobot Servo Controller but I think the following tutorials can help you with the serial communication on the Raspberry Pi’s side:
On the servo controller’s side, I can’t help much, the user manual says “Please read the secondary development documentation for a full understanding on how to use the servo control secondary development instruction” but I couldn’t find that. What I suggest is checking out the C++ file on the LSC series communication routines file as well as checking the Arduino examples available in that same file.