Switch – missing Packet tracer physical Tab

You have multiple things that could cause this:

• Daisy-chaining PCs will be a problem since they are not optimized for switching. The PCs closest to the switch will need to handle their own traffic as well as all the traffic from the PCs behind them.
• You can cause congestion if the uplink from the switch is the
  same speed as each of the links from the PCs feeding it. Multiple,
  saturated access links simply cannot be served at line-speed by a single
  uplink at the same speed as the access links without congestion. The switch uplink needs to be at least as fast as the aggregated access links' speeds.
• You should check the load on your router since it may have gigabit ethernet ports, but that doesn't mean it can packet switch at line-speed, especially with multiple services running on it.
• The link to the server needs to be at least as fast as the aggregated access links' speeds.

You need to figure out what is causing the congestion and remediate it, and there may be multiple problems that need to be resolved. That may involve redesigning your network, replacing underpowered equipment, upgrading link speeds, etc.

That's not a node, that's a cloud representing the Internet. You have no way of knowing how the Internet is connected, so it is represented as a cloud. It represents a whole lot of nodes.