Recommendations for Certs/Classes to better understand troubleshooting networks.

For instance, when I get a complaint of network slowness, i usually start by checking link speed and replacing things on the physical layer, by swapping cables, reterminating / replacing jacks, swapping ports. Id like to learn more in depth troubleshooting like finding network loops easier, learning to utilize wireshark to its full potential and how to understand what im looking at. Best place to install wireshark or read the traffic logs on our firewalls without google searching ecerything. What certs or classes should i pursue if my job is willing to pay for them.