Performance issue when running in Kubernetes

I have just tested with a limits.cpu=4000 and +S 4 and there is no more spikes. Everything run perfectly. Thank you !!!
I am new to Kubernetes and I was definitely not understanding how to set the values in cpu.

I have now

requests:
  cpu: 1
limits:
  cpu: 4

Is it fine to have limits.cpu set to the node number of core to make sure my app won’t be throttled ? Won’t it be risky for other pods running on the same node to have my app potentially using too much of the cpu ?

And, what would be the reasoning to do to chose the value for requests.cpu ? I guess if I set it too high, I might end up having a node underused because less pods would be scheduled on it.