Troubleshooting a slow internet connection in a large office building involves:

1. Identifying the source of the issue – external or internal
2. Checking if the number of users on the network has exceeded capacity
3. Updating the router’s firmware and restarting the router
4. Using Speedtest to test the download and upload speeds of the network
5. Checking the network for malware, viruses and/or spyware
6. Verifying that the infrastructure is still setup and properly configured