is truncated request loss in payload and what is danger or risk from truncated request?

some more information will be needed, where do you see this and how is the F5 BIG-IP involved in this? which module(s)?

im kinda assuming ASM, in that case truncated is normal if the request is larger then 2kb (i believe), just because you don't want to log huge requests. response timeout is an issue, that just means the response has taken too long, does the application work at all?